147 and to emphasize the significance of the active intermediate in the thermodynamic coupling. This might dispel the confusion of those students who have studied the textbook assignment and yet wonder - - if the hydrolysis of A T P is a futile reaction, how can it drive an unfavorable reaction? - - but are too timid to ask.
R
o c.t
:"
oo-.Lo. H--C--OH CHzOPOs
NsC~-c~N.~
U 0%/~'~ P--OH
I
l
Oe~,,,~ °
I
phate' as described in this article has been limited arbitrarily to include a representative, albeit incomplete, sampling of those currently available.
NH2
0
c
Note: The list of textbooks that use 'high-energy phos-
H--C--OH
o
II
0--
I
CH
HC%N/C"N
O
o
I
CH2OPO~
II
OH
OH
+
H--C--OH
~H2 o
O
O
O
II
II
II
HC%N/C'~N
- - P - - O - - P - - O - - P--O--CH2 ~
I
I ,
OH OH Figure 2 Phosphoryl group transfer to A D P yields A TP. Inorganic phosphate becomes the eventual source of a phosphoryl group when a phosphate ion, HOP032-, replaces a hydride ion, H 2-, as glyceraldehyde 3-phosphate is oxidized to 1,3-bisphosphoglycerate (1,3-BPG). Nucleophilic attack by A D P on the high-energy intermediate, 1,3BPG results in the conversion of A D P to A T P as an 02moiety of the phosphate group leaves as part of the product, 3-phosphoglycerate. The 02- moiety is stippled to emphasize these transformations refer to 'hydrolysis of A T P ' as the driving force for the coupled reaction without emphasizing that the actual source of atoms for the hydrolysis is the substance that is transformed into activated intermediate, not a water molecule. Perhaps, one should refer to 'cleavage of phosphorylated intermediate' (or pyrophosphorylated, or adenylated intermediate, etc) as the driving force for the coupled reaction, to avoid any reference to hydrolysis
BIOCHEMICAL
E D U C A T I O N 20(3) 1992
References 1Lipmann, F (1941) Metabolic Generation and Utilization of Phosphate Bond Energy, Adv Enzymol 1, 99-162 2Lipmann, F (1971) Wanderings ofa Biochemst, John Wiley and Sons, New York 3Kalckar, H M (1969) Biological Phosphorylations, Prentice-Hall, Englewood Cliffs, NJ 4Watson, J D, Hopkins, N H, Roberts, J W, Steitz, J A and Weiner, A M (1987) Molecular Biology of the Gene, Fourth Edition, Benjamin/ Cummings, Menlo Park, CA 5Mathews, C K and van Holde, K E (1990) Biochemistry, Benjamin/ Cummings, Menlo Park, CA 6Stryer, L (1988) Biochemistry, Third Edition, W H Freeman and Co, New York 7Darnell, J, Lodish, H and Baltimore, D (1990) Molecular Cell Biology, Second Edition, W H Freeman and Co, New York 8Alberts, B, Bray, D, Lewis, J, Raft, M, Roberts, K and Watson, J D (1989) Molecular Biology of the Cell, Second Edition, Garland Publishing, New York °Friedman, P J (1992) Biochemistry: A Review with Questions and Explanations, Fourth Edition, Little, Brown, and Company, Boston H)Southerland, W M (1990) Biochemistry Churchill Livingstone, New York ]lAkers, H A and Smith, E H (1987) Problems with Phosphate Abbreviations, Biochem Educ 15, 78-79 12Rawn, J D (1989) Biochemistry, Nell Patterson, Burlington, NC 13Voet, D and Voet J G (1990) Biochemistry, John Wiley and Sons, New York ~4Walsh, C (1979) Enzymatic Reaction Mechanisms, W H Freeman and Co, New York
Biological Chemistry (Second Edition) by T T Berezov and B F Korovkin (in Russian). pp 543. Textbook for medical universities, Moscow. 1990 The first edition of this text for medical students (1982) was reviewed in Biochemical Education [12, 90 and 185] and was recommended by the USSR Ministry of Health for all 87 Medical Institutes throughout the country. A second extended and updated edition has now appeared.