Enzyme inhibition by palladium chloride

Vol. 35, No. 3, 1969

BIOCHEMICAL

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

ENZYME INHIBITION

BY PALLADIUM

John D. Spikes Department

and Carol

Salt

F. Hodgson

of Biological

University Lake

CHLORIDE*

Sciences

of Utah

City,

Utah

84112

Received April 9, 1969 In the

course

sensitizers that

for

of examining

the photodynamic

palladium

(+2)

and to interfere literature carried

out

several

enzymes.

plant

action

was assayed

was then

added

intervals

for

as described hydrogen

alpha-chymotrypsin; peroxide

3'-cyclic (BAEE)

phosphate for

(4), (7),

examination

phosphate at zero

time; of the

papain

references

for

catalase; lyophilized

coupled for

with

(5) not

o-dianisidine

ribonuclease;

reason

we (+2)

incubated

in a 15'C.

water

or 4.2. -3

removed

carried (8).

acetyl-L-tyrosine Micrococcus

in the

of palladium

were

under

(6),

effects

0.5 ml of 2 x 10

listed

fibroin

any reports

For this

of pH 8.9

were

we observed

to proteins

and silk find

inhibitor.

mixture

(2),

by a non-photochemical

we did

buffer

as possible

shown to bind

of the

Enzyme assays

20 min.

peroxide

hydrogen

growth

and samples

in the

directly

of 80 uM - enzyme were

0.5 ml of sodium

activity

casein

(1)

of enzymes

has been

as an enzyme

a preliminary

One ml quantities with

(+2) (3),

with

on its

trypsin

palladium

such as carboxypeptidase

porphyrins

inactivation

inactivated

Although

process.

palladium

out

_M palladous for

chloride

assay

at 5 min

spectrophotometrically

ester

lysodeikticus for

bath

The enzymic

The substrates ethyl

on

for

peroxidase;

and benzoyl-L-arginine

used were: (ATEE)

for

lysozyme; cytidine-2', ethyl

ester

trypsin.

*This work was supported No. AT(ll-l)-875.

by the U.S.

Atomic

420

Energy

Commission

under

Contract

Vol. 35, No. 3, 1969

BIOCHEMICAL AND BlOPHYSlCAl

Of the enzymes inactivated

listed

above,

by palladium

as shown in Fig. at pH 4.2,

but

was not

very

inactivated

fairly

inactivated

rapidly

were

and pH-dependent

time-

was very

at pH 8.9. but,

and trypsin was

trypsin

at pH 4.2,

rapidly

chymotrypsin

The inactivation

(+2).

As may be seen,

1.

inactivated

only

RESEARCH COMMUNICATIONS

rapidly

inactivated

Alpha-chymotrypsin

in contrast

to trypsin,

was also was

at pH 8.9.

D--o--o---o---o\

,TRYPSIN

TRYPSIN

IpH 8.9)

(pti 4 21

I I I I /-wC*Y~~~TF~YPS.IN

bH4.2)

Figure 1. Inactivation of trypsin and alpha-chymotrypsin by palladous The reaction system was 40 uM in enzyme, chloride at pH 4.2 and 8.9. 5 x 10% in palladous chloride and 0.125 M in sodium phosphate buffer. There was no loss of enzyme activity underthe conditions described in the absence of the palladous chloride.

The mechanism palladium

(+2)

divalent

form

is not also

trypsin

by reacting

mercury

may inactivate

by forming

of the

a stable

inactivation

known.

Other

of chymotrypsin metals

inhibit

these

with

sulfhydryl

groups.

chymotrypsin

(which

chelate

with

enzymes

the

(copper, (9);

zinc,

mercury It

mercury)

presumably

has been

has no free

active-site

421

and trypsin

histidine

suggested

sulfhydryl (10).

by in the inhibits that groups) Palladium

Vol. 35, No. 3, 1969

(+2)

binds

which with

BIOCHEMICAL

to papain

suggests

with

that,

sulfhydryl

for

groups

L-cystine

and Lmethionine

one could

envision

free

sulfhydryl

of chymotrypsin

that groups might

the

same stoichiometry

this (5).

enzyme,

solution,

but

(+2)

as does mercury

binding

(+2)

palladium

result

its

Palladium in

and/or

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

is

forms

inactivates

with

cystine

from

reactions

with

L-histidine trypsin

groupings with

due to interaction

complexes

not with

(+2),

(11).

by combining

, while

cystine

L-cysteine,

the

Thus with

inactivation

groupings.

References 1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11.

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