Regulation of trout gill AMP deaminase by lipid bilayers. Effects of phospholipid composition and temperature

pp. 685-692, 1985

N OF TROUT GILL AM LAYERS. EFFECTS OF ] 'OSITION AND TEMPER ~-AFFIN,t3~JADWIGA PURZYCKA-PREIS,~ /IICHAL WOZN1AK§ and MARIUSZ ~VO e Comparre des Rrgulations, C.N.R.S., 67037 Strasbourg Crdex, France; and §Department of Biochemistry, Bit 80-211 Gdansk, Poland

IINASE DLIPID

)ess, B.P. 20 CR, ol, ul. Debinki 1,

(Received 16 July 1984) Abstract--1. Trout gill AMP deaminase is inhibited by liposq aosomes made containing higher saturated fatty acids. A preincubation of o 1 hr, at 4 maximal effect. 2. At 4 or 25°C,. these phospholipids modified essential tiaUy the sub increasing the Michaelis constant proportionally to the length le: of th~ liposomes decreased the Hill coefficient also, thus inducing a negative 3. Natural phosphatidylcholine and phosphatidylserine were withot deaminase while natural sphingomyelinexhibited a similar effect eft to that .~ phosphatidylcholines. 4. These results are discussed in relation to a possible ef effect of sphi

INTRODUCTION

osphatidylcholines sary to obtain the of the enzyme by ain. At 13°C, the ffect on gill AMP esence of synthetic vivo.

the pJ )roduction of adenosine at the membrane interface. We report here the effects of phospholipid phos bilayers (lipos (liposomes) of different compositiol ~osition on the properties ties ol of trout gill A M P deaminase. The Tt results suggest that s] sphingomyelins containing high~ her saturated fatty acids could play a role in the re~gulation of the intrac acellular A M P deaminase in gill ill.

Hi gh A M P deaminase[I (AMP aminohydrolase; EC 3.5.4.6 i.4.6) activities are found in the gills of several species ~cies of fish (Makarewicz and 2ydowo, 1962; Makarewlcz ~wicz, 1963; Raffin and Leray, 1980). Recently, the purification rification and properties of trout gill A M P deamlnase finase were reported (Raffin, 1984). The enzyme wasLSshown to display very particular kinetic properties with respect to the effect of of substr substrate, monovalent cations and nucleotides. Besides its well-known particil: lrticipation in the regulation of adenylate energy charge (Chapman and Atkinson, 1973), A M P deamin iminase could play an important role in the regulation ion of the availability of A M P for dephosphorylation by 5'-nucleotidase, thus regulating the production of• adenosine, a mediating he coronary blood flow factor in the regulation of the (Berne, 1964). Adenosine wass also shown to regulate the branchial blood flow in the trout (Colin et al., 1979). It was shown, in various tiss ~sues, that the regulatory properties of A M P deaminas~ rose are modified in a specific way by phospholipid bilayers (Purzycka-Preis et al., 1978; Prus et al., 19800; ~ydowo et al., 1980). enzyme molecules which Thus, one may suspect that enz, are in close contact with the le membrane should be more susceptible to participate ate in the regulation of

Enzyme preparation the gill of rainbow AMP deaminase isoenzymes from th trout (Salmo gairdnerii R.) were purif mrified as previously described (Raffin, 1984). Only peak II was used for this study.

*Part of this work was supported :ed by a FEBS Fellowship and by Polish Ministry of Sciences and Higher Education within the project R.I.9., 1.9., 01,06. :~Correspondence to be addressed sed to: Jean-Paul Raffin, Laboratoire de Biologie Marine fine du Coll~ge de France, B.P. 38, 29182 Concarneau, France. IlAbbreviations: AMP, adenosine-5'-mono DL-dithiothreitol.

Enzyme assay Enzyme activity was assayed by estim estimation of ammonia liberated from AMP. About 1-5/~g of enzyme protein were diluted in 1 ml of liposome suspension containing 1.5 #mol pmc of phospholipid phosphorus, 0. I mM potassium succmate succinatc pH 6.5, 150mM pension was preincubated eaction was started by the assium succinate pH 6.5,

MATERIALS AND METH( METHODS Materials AMP, DTT, egg yolk phosphatidLylcholine, bovine brain phosphatidylserine, bovine brain brai sphingomyelin, dimyristoyl-phosphatidylcholine,dipalmi palmitoyl-phosphatidylcholine, distearoyl-phosphatidylcholine, dioleoyl-phospha-phosphatidylcholine and tidylcholine, fl-oleoyl-~,-palmitoyl-phosp dipalmitoyl-phosphatidic acid were from fron Sigma Chemical Co., St Louis, MO, USA. Dimyristoleoyl-phosphadipalmitoleoyl-phosphat tidylcholine, hosphatidylcholine and fl-palmitoyl-~,-oleoyl-phosphatidylcholim lcholine were from Avanti Polar Lipids, Inc., Birmingham, USA. All ,~ other chemicals were analytical reagent grade materi materials from Merck, Darmstadt, FRG.

JEAN P. RAFFIN

ng different amounts out at 4, 13 or 25°C, icon autoanalyzer on er to be controlled by , seven samples were by the addition of the :t for ammonia estiWhen necessary, the o use, in 50mM dimg/ml bovine serum citric acid. The final mixture was 0.5mM, ffin, 1984). 9ne unit of AMP deaminase is defined as the amount of 'yme deaminating 1 ttmol substrate/min in our experintal conditions,

!culation of kinetic parameters ['he kinetic parameters were calculated by using a nonmr regression method. The experiments were repeated at ~t twice, and the data were plotted as previously deibed (Rattin, 1984),

,paration of phosphatidylcholine from trout gill Ananaesthetized fish were decapitated just posterior to opercula and the head was rapidly immersed in 21 of ine solution (9 g NaC| and 320 U.S.P. units heparin/1) in ler to wash out the major part of the blood. The gill hes were excised, gently blotted dry, and the mucosa apped with a scalpel. Total lipids were extracted in mixture as described by Di Costanzo ~ = = a oroform/methanol vx v=v~==, d. (1983). Phosphatidylcholine was separated by preparaet al. tire thin-layer chromatography (silicagel F-254, Merck) usinng chloroform/acetic acid/H20 (50:30:8:4, v/v) as mobile phase.

125

et al.

Preparation of lip Liposomes con were prepared as

nt kinds of phospholipids 'urzycka-Preis et al. (1978). rs es on A M P deaminase if the enzyme was preme in the presence of the • A t saturating substrate lylcholine activated gill dipalmitoyl-phosphainhibitory effect. iments a p r e i n c u b a t i o n hr p r e i n c u b a t i o n of the osomes induced a 2-fold h o u r effect o n g m a n d h n the absence of ATP, 01k phosphatidylcholine f Vm~~ (Fig. 3). In the mes were without effect s indicate t h a t egg yolk ing liposomes are withtminase since the slight ice of A T P could r a t h e r t o f the liposomes during

A n effect of activity was de i n c u b a t e d for a p h o s p h o l i p i d ve conch, egg yol] AMP deamin tidylc] lcholine exe Fol F o r all subs, time cof 1 hr wa! 'me in the a enzyn decrease o f Vm, decre~ (Hill coefficient ~osomes cont~ lipose luced a slig[ induc, preselnee of A T o n the th enzyme. )hosphatidylch, phosl: out effect e on incre~ Increase of V~a~ be be du~ due to a stabJ the plvreincubati, ~remt:uoauun.

Effects o f liposomes made with d ifferent kinds of phospholipids pho As it was s h o w n for egg yolk phosphatidylcholine, containing liposornes trout gill p h o s p h a t i d y l c h o l i n e cont

[

1

~ o

'~. 0

.~_

50

,v

I

0

10

30 Preincubotion

4O

time ( min )

Fig. 1. Influence of pre•eincubation time on the effects of liposomes of trout gill AMP dear~tinase. The lcholine (C)) ted, at 4°C, in the absence (Q) or presence of egg yolk phosphatidylc enzyme was preincubated, bation times, AMP or dipalmitoyl-phosphatidylchol ed in Materials and deaminase activity was determin

ion of trout gill AMP deaminase by lipid

0.125[ 0.100

00 .75

/

J

0.0~

0.025 |

i

-2

"1

o

,~ !

1

~

!

J

4

5

1IS Fig. 2. Effects of preincubation on the kinetic properties of o trout gill AMP deaminase. The,enzyme was preincubated (O) or not preincubated (0) for 1 hr, at 4°C, 4°C in the absence of liposomes, as cdescribed in Materials and Methods, and the AMP deaminase activity was determined, at 25°C, in 0.1 M potassium succinate pH 6.5, 150mM KC1, 0.1 mM DTT, containing containi different conchs of AMP, by measuring ammonia liberated according to the method of Chaney and Marbach (1962).

were without effect on the gill enzyme (Fig. 4). However, if the liposomes were made with bovine brain phosphatidylserine, at 2-fold decrease of Vma~ was observed while K mand h were unchanged. Bovine tsed the K~ significantly brain sphingomyelin increased (from 1.6 to 2.7 raM), while V~x was unchanged. The double reciprocal plot showed ed a dow downward townward deviation deviation, indicating a negative cooperativity rativity as further demonstrated by a drop of h fromn 0.94 to 0.73. These results show that the le polar head group of the phospholipids plays a role inn the effects of liposomes on trout gill AMP deaminase.

Effects of liposomes made with phosphatidylcholines containing different kinds ofrfatty fall acids The effect of the fatty acid :id structure of the phospholipid was investigated by using synthetic phosphatidylcholines containing: different kinds of fatty acids. When the phospholipids contained only saturated fatty acids, the liposomes exerted certed an inhibitory effect depending on the length of the fatty acids (Table 1). toline had Dimyristoyl-phosphatidylcholine ha no effect on gill AMP deaminase, while dipalmito >almitoyl and distearoylphosphatidylcholine containin aing liposomes increased the Kin. These phospholipidss had no significant effect on Vmaxand h. Phosphatidylcholines containing t acids of different length were withe

deaminase (Table 1). kinetic kine! properties of gill AMP dea Thus, liposomes made with phosphatidylcholines containing saturated fatty acids with wi a chain length of at least 16 carbons, inhibited the I gill AMP deaminase by decreasing the affinity for the substrate. dcholines containing one The effects of phosphatidylcholin saturated and one unsaturated fatty fatt acid are shown in Fig. 5. fl-Oleoyl-7-palmitoyl-ph toyl-phosphatidylcholine did not affect the kinetic propertic )erties of the enzyme. However, the symmetrical molecular form, fl-palmitoyl-7-oleoyl-phosphatidylc dcholine inhibited the enzyme in a similar manner to t, that shown for phosphatidylcholines containing only on saturated fatty acids. The Km increased from 1.6 to 2.8 mM, while Vm~ and h were unaffected. These results show that the fatty acid located at the fl position of the phospholipid is recognized l by the gill AMP deaminase and that this fatty f~ acid has to be saturated in order to exert an effect eff¢ on the kinetic properties of the enzyme.

~erature on the effects Influenceof the incubation temperaJ of liposomes The preincubation temp could not easily be increased without dramatic loss of enzyme activity. Thus, only the incubation temp was changed from ion temp of the animals). cc of liposomes, the Hill 1an 1.0 indicating a slight

JEAN P. RAFFINet al.

120

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> T,=

0.030

,/

-1

o

1

Z

1 /5 Fig. 3. Effects of egg-yolk phosphatidylcholine-containing liposomes 1 and ATP on the kinetic properties of trout gill AMP deaminase. After a preincubation of the enzyme, el at 4°C for 1 hr, in the absence abse~ (closed symbols) or presence (open symbols) of egg-yolk phosphatidl )hatidylcholine-containingliposomes )mes (see (se~ Materials and Methods), the AMP deaminase activity was determinec determined as described in the legend of Fig. Fi~ 2, in the absence (0, ©) or presence (A, A) of 1 mM ATP.

COO operativity

(Table 2). At this temp the Km "~ is about phatidylcholines from egg yolk or ( trout gill are two times lower than at 25°tE. At l 3°C, these kinetic without effect on gill AMP deamina eaminase. The inhibition of this constants are the same as those ose determined at 25°C. enzyme by fl-palmitoyl-7-oleoylDimyristoyl-phosphatidylcholine :holine had no effect phosphatidylcholine suggests that oonly the fatty acid at 4°C, as already demonstrated Lstrated at 25°C, while at position fl is recognized by the enzyme and that to obtain an effect dipalmitoyl- and distearoyl-tphosphatidylcholines in- this fatty acid has to be saturated tq Distearoyl-phosphatidyl- on the kinetic properties of gill AMP Ah deaminase. A creased the Km at all temps. Distearo dcholine in which the choline induced a decrease', of Vm,x essentially at molecular form of phosphatidylcho 13°C where this parameter was reduced by 50~o. saturated fatty acid is located at the fl position exists dso decreased the Hill only in very small concns in natural membranes. This These two phospholipids also coefficient, restoring a normal al Michaelien behaviour can explain the lack of the effect of natural phostme. at 4°C, and inducing a negatwe ~gative cooperativity at phatidylcholines on the gill enzyme longer 13°C. Sphingomyelin increased sed the Km but did not The fact that only phospholipids containing q fatty acids inhibit gill AMP deaminase deal could be decrease the Hill coefficient. explained by a steric effect, a minimal mini chain length being necessary to obtain an interaction interac with a more DISCUSSION or less buried hydrophobic site on the t enzyme moleification of the ternary ,~ffects of liposomes on cule, or to obtain a modificatior Previous works on the effects AMP deaminase used natural •al phospholipids (phos- structure of the enzyme. of the phosAn effect of the molecular structure strucl phatidylcholine, phosphatidtylethanolamine, phosis et al.. al., 1978; Prus et al., pholipid itself, which depends on the incubation phatidic acid) (Purzycka-Preis temperature, seems improbable for different reasons, 1980; ~ydowo et al., 1980). These phospholipids are effect of dimyristoyla mixture of different molecular forms with variable It was not possible to detect any effe ncubated under or near aajor molecular form for phosphatidylcholine either incubat~ fatty acid composition. The ma abot 24-25°C (Hinz natural phosphatidylcholines is fl-oleoyl-y-palmitoyl- its transition temp which is of about 3olde and Van Deenen, and Sturtevant, 1972; Oldfield and Chapman, 1972), phosphatidyl choline (Van Golde :oyl-phosphatidylcholine 1966; Holub and Kuksis, 1978; Hi ~r their transition temps saturated fatty acid being thereby loc urtevant, 1972; Papa~. This molecular form as well as

n of trout gill AMP deaminase by lipid b 0.4

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0.3

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1IS Fig. 4. Effects of liposomes containing different kinds of phospholipids ph( on the kinetic propertit ~erties of trout gill AMP deaminase. After a preincubation of the enzyme, at 4°C for 1 hr, in the absence (Q) ( t ) or o presence ~hosphatidylserine(A) or bovine brain sphil of trout gill phosphatidylcholine (©), bovine brain phosphati ;phingomyelin (&)-containing liposomes (see Materials and Methods), the AMP deaminase activity was dete determined as described in the legend of Fig. 1. phospholipid isomers differ only bby a few degrees phos[ "Szoka and Papahadjopoulos, 1980)) and the transi(Szok palmitoyl-phosphatidyltion temp of fl-oleoyl-?-palmitc choline is under 10°C (Stubbs et aL, 1981), the differences observed between this inactive phoslines containing different kinds Table 1. Effects of phosphatidylcbolines pholipid and the active fl-palmitoyl-?-oleoyles of trout gill AMP deaminase of fatty acids on the kinetic properties phosphatidylcholine cannot be explained by a determined at 25°C lso be the case for conformation effect. This should als betwee~ phosphatidylK~ the differences observed between Composi t i on Vmax cholines containing either only saturated or only (mM) of ]iposomes (pmol/min/ml) desaturated fatty acids. )id vesicles on trout Thus, the effects of phospholipid 1.60 0.94 -47.9 specific, not gill A M P deaminase seem to be rather ra of the phospholipid depending on the conformation 1.5£, 0.99 OMPC 46.5 also depends or the stability of the liposomes, which wl~ 2 . 5 0 0.93 DPPC 46.6 on the nature of the fatty acids, since sin phospholipids containing larger saturated fatty acids a are able to 3.13 1.11 DSPC 40.8 aggregate more or less rapidly. We could not detect 1.25 0.90 DMOPC 38.3 were any significant difference if the experiments e the preparation of 1.43 0.93 performed either immediately after t] DPOPC 40.9 the liposomes or several hours later, lateJ indicating that DOPC 54.8 1.25 0.88 the results can probably not be explained by a clustering of enzyme molecules in lip)osome agregates. After incubation of the enzyme, for• I hr at 4°C, in the presence of Another observation in favour of o a specific effect liposomes (see Materials and Methods dethods), the AMP deaminase o f liposomes on A M P deaminase is the fact that h4 potassium succinate pH 6.5, activity was determined in 0.1 M effect on the dipalmitoyl-phosphatidic acid is without witl 150AM KCI, 0.1AM DTT, containing different eoncns of ~rated according to the method e n z y m e (result not shown). Thus, the polar group AMP, by measuring ammonia liberated of Chancy and Marbach 0962). Abbreviations: DMPC, talavs an imnortant role in the inte the interactions between dimyristoyl-phosphatidylcholine; DPPC, di ipid. The positive charge dylcholine; DSPC, distearoyl-phosphatid n seems to be important dimyristoleoyl-phosphatidylcholine; DPO tic effects of phosphosphatidylcholine; DOPC, dioleoyl-pho haddjopoulos et al., 1975) and 59°C (Hinz and Sturtant, 1972) thus being in a "liquid crystal" conevant. rm~tinn However, blnwever_ smce ~inee the transition tem[ temtgs of formation.

JEAN P. RAFFIN el al.

/

OJ5

//

0.10

,-

D

O.O

0

-1

A~//o o

1

2 1/S

3

5

4

Fig. 5. Effects of liposomes made with phosphatidylcholi dcholines containing one saturated and cone desaturated fatty acid on the kinetic properties of trout gill AMP deaminase. d The experimental condlitions were the ~reincubated in the gill AMP deaminase was preir same as described in the legend of Fig. 4, except that trout tr, 'lcholine (O) or -palmitoyl-phosphatidylcholi absence ( 0 ) or in the presence of /~-oleoyl-'f /7-ole ¢lcholine (A)-containing liposomes. #-palmitoyl-7-oleoyl-phosphatidylcho

Table 2. Effects of liposomes on the kinetic properties of trout gill A M P deaminase determined at 4 or 13 C Compos i t i on

I ncubati

of

temperature

1 i posomes

on

Vma x (pmol /mi n/ml )

Km

h

( mM )

4 C

13.1

0.85

1.37

13 C

20.4

1.73

C.96

DMPC

4 C

18. I

O. i ; l

L . 21

DPPC

4'C

15.]

1.5

1.03

DPPC

13 C

15.

2.03

[! ,,~13

DSPC

4 C

9.4

2.52

0.91

DSPC

13 C

6.4

4.29

0.74

SPH

4'C

9.2

1.68

1. 12

SPH

13 :C

16.9

2.77

1. 17

1

After preincubation of the enzyme, at 4'C for 1 hr, in the presence o f liposomes (see Materials and Methods), A M P deaminase activity was determined, at 4 or 13~C, in 0.1 M potassium succinate p H 6.5, 150 m M KCI, 0.1 m M D T T , containing different concns o f A M P , by measury and ing atidylMar ~aroylchol phos

lation of trout gill AMP deaminase by lip myelins. Natural ic properties of gill aat which was demitidylcholines. This le composition of ntain mostly saturtic acid representing )rain sphingomyelin

epithelium wh( racellular structures are well developed d Dunel, 1980). In trout gill, lins could play a role in the regulation minase since they represent 6--8~ of t ibraneous phospholipids (Abdul-Malak, ~cessibility of the enzyme to the fatty ac t the outer layer of the membrane cou ed by the fluidity of the membrane as w kness of the lipid bilayer. This thickness regulated by the membrane potentia Lson et al., 1979) which should be sul 5ations during salinity chanlges (Evans Th Thus, the i between gill A M P deamin ammase and th aabrane could play a role in the th, adaptati ons in external salinity. The modificati : ~MP deaminase activity durinLg variatio ucture of the membrane indue by the: induced anges could improve the reguL ulation of e energy charge under condi conditions of it gy consumption. Such a stabil stabilization of :harge in spite of a dramatic decrease oncn and the ATP/ADP ratio,, was dem ring adaptation of trout to sea-water se~ (I_ 981). The interaction of gill AMP ,~ dean aembrane phospholipids could also all( allow the access of th the enzyme to an actiw activating proteinase demonstrate ,nstrated in that tissue (Raft Raffin, 1981). Finally, as suggest :ested for pig heart AMF A M P deaminase (Purzycka-Preis et ( al., 1978), the inter~ interaction of the enzyme with the membrane could play a role in the regulation of the tl production of aden( adenosine, a regulator of branchial Iblood flow (Colin et al. al., 1979). However, inversely to tc that which was deme demonstrated in other tissues, lilposomes do not modi the effect of ATP on gill A M P deaminase, modify ATP being without effect in the pz 9resence of monovalent cations (Raffin, 1984).

lyelin on trout gill those obtained with containing higher turated fatty acids when the effects on K m are ncerned. These effects differ nevertheless for the ill coefficient, sphingomyelin inducing a negative operativity at 25°C. The effects of the liposomes on e Hill coefficient seem to depend, more than the Fects on Km on the incubation temp, while the crease of the affinity for the substrate is dependent ther on the preincubation time and temp. In this Jdy, only the incubation temp was changed since e preincubation temp was imposed by the stability the enzyme. During the preincubation in the ,sence of liposomes, a drop of Vm~ was observed, ms, the increase of Vm,x observed, under these nditions, in the presence of egg yolk phosmtidylcholine should rather be due to a stabilizing !ect of the liposomes during the preincubation, Chan ranging the incubation temp will induce tempeffects on the enzyme molecule itself with a modification adification of the Hill coefficient. At 4°C, gill AMP deaminase aminase displays a slight positive cooperativity which lich is not visible at 13°C (acclimation temp of the animals imals) or at 25°C. The liposomes will change this tem aap effect on the Hill coefficient in a less fatty-acid related fashion. Thus it is possible to distinguish the effects of the liposomes ,osomes on the Hill coefficient and on the affinity :y for the substrate. The effe:cts on the Km are the consequence of a specific hydrol: hydrophobic interaction Acknowledgements--The authors thankk Mrs G. Gutbier he fatty acid while the and H. Grabicka for skilful technical assistance. Dr C. between the enzyme and the at are more probably a Leray is gratefully acknowledged for his support during the effects on the Hill coefficient modification of the temp induced nduced changes on the work. enzyme molecule. REFERENCES The interactions between the liposomes and trout gill A M P deaminase require ire a rather long pre- Abdul-Malak N. (1978) Etude au moye cen de radiotraceurs incubation time, suggesting the existence of du metabolisme des phospholipides des de tissus de la truite modifications in the structure re of the enzyme and/or arc-en-ciel (Salmo irideus). Effets de la salinit6 et de la temperature. Thesis, Universit6 Clau(de Bernard, Lyon, liposomes. Since the effects of phospholipids include France. interactions with the fatty acids, ids, the enzyme molecule blood flow. ,~ss deeply into the lipid Berne R. M. (1964) Regulation of coronary cor should penetrate more or less Physiol. Rev. 44, 1-29. bilayer. In natural membranes nes, phospholipids seem Bloj B. and Zilversmit D. B. (1976) Asy ;ymmetry and transto be disymmetrically distributed ibuted between the two position rates of phosphatidylcholine in rat erythrocyte phospholipid layers. It was demonstr ~strated emonstrated, in erythroghosts. Biochemistry, N.Y. 15, 1277-1283. 1277-1 cytes, that phosphatidylserines and phos- Calhoun W. I. and Shipley G. G. (1975)) Fatty acid comphatidylethanolamines are predomin redominantly located on position and thermal behaviour of natural na sphingomyethe cytoplasmic layer of the membrane while phoslins. Biochim. biophys. Acta 555, 436--441. 436phatidylcholines and sphingom) omyelins are rather dis- Chaney A. L. and Marbach E. P. (1962))Modified reagents for determination of urea and ammornia. Clin. Chem. 8, tributed on the outer layer (Verkleij et al., 1973; ;rg et al., 1974; Gazitt et 130--132. Zwaal et al., 1973; Kahlenber (1973) Stabilization of ~5; Bloj and Zilversmit, Chapman A. G. and Atkinson D. E. (19~ al., 1975; Zwaal et al., 1975; adenylate deaminase have t< to be confirmed on adenylate energy charge by the ad~ 1976). However, these results have reaction. J. biol. Chem. 248, 8309-831 ~309-8312. other tissues. In addition, nothing thin~ is known about the ,~^,:_,-, A v:_+_L . . . . . . . . . . . . . . ¢ C. (1979) Haemodynamic distribution of the phospholipids in of the trout (Salmo gaimembranes which could play an impc 130, 325-330. regulation of A M P deaminase, espe( .eray C. and Nonnotte L.

JEAN P. RAFFIN et al. organization of the bow trout intestine. f ion transport by fish ~, R 224-R 230. • (1975) Changes in d phospholipases ind amphibian erythroActa 382, 65-72. 9ell B., Steingrimsdot:lson S. (1979) Docospholipids and ionic rnational Society .for Uardiological Research", Dijon, France. .zel J. R. (1979) Influence of thermal acclimation on nembrane lipid composition of rainbow trout liver. Am. L Physiol. 236, R 91-R 101. az H. J. and Sturtevant J. M. (1972) Calorimetric studies 9f dilute aqueous suspensions of bilayers formed from ;ynthetic L
ty of phosphotipid bilayers, erties. 1. Chant Biochim. bioph ~04-519. Prus E., Purzyck szniak M. and Zydowo M. (1980) Purific~ ulatory properties of pig ota hiochim, pol. 27, 241kidney AMP 248. )zniak M. and Zydowo M. Purzycka-Preis, J (1978) Modifi osomes of the adenosine t on adenylate deaminase triphosphate-a~ 175, 607 612. from pig heart inase from trout gill: localRaffin J. P. (198 }teinase. Molec. Physiol. 1, ization of the 223-234. and properties of trout gill Raffin J. P. (198, Raffia AMP AM deamina ~hysiol. B. 154, 55-63. Comparative study of AM P Raffin J. P. and L Raffin md blood of fish. Comp. deaminase in ~40. Bio, Biochem. Phys inosita K. and lkegami A, Stubb C. D., K Stubbs on the dynamic properties (191 Effect o (1981) ! lecithin bilayers. Biochemof the t hydroca istr~T, N.Y. 20, 9s D. (1980) Comparative Szoka F. and F weparation of lipid vesicles properties and pr O Bioeng. 9, 467-508. (lip~,osomes). A )eenen L. L. M. (1966) The L. M Van Golde ( aolecular species of lecithin effect effe, of dietar ~),s. Acta 125, 469-509. from fror rat liver. Roelofsen B., Comfurius P., Verkleij Verkk A. J., Zv Kastelijn D. and Van Deenen k L. M. (1973) The Ka, aids in the human red ass3/metric distribution of phospholipi using phospholipases cell membrane. A combined study us and freeze-etch electron microcopy. Biochim. biophys. Acta 323, 178-193. Colley C. M. (1973) Zwaal R. F. A., Roelofsen, B. and C Biochim. Localization of red cell membrane constituents, co Loc biophys. Aeta 300, 159-182. mfurius P. and Van Zwaat R. F. A., Roelofsen, B., Corn Zwaal Dee Deenen L. L. M. (1975)Organization of phospholipids in Ls detected human red cell membranes as detect~ by the action of hun biophys. Acta various purified phospholipases. Biochim. Bim vari 40@ 83-96. T. (1980) Zydowo M., Walentynowicz O. and Wrzolkowa W AMP deaminase from the rat heart inljured by high doses of vitamin D. Acta biochim, pol. 27, 233-240.