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THE FUNCTION OF PHOSPHATE IN CELLULAR ASSIMILATIONS
Author(s) -
M. KALCKAR H.
Publication year - 1942
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1942.tb00430.x
Subject(s) - chemistry , pyridine , enzyme , phosphate , medicinal chemistry , organic chemistry
Summary Two different types of carbonyl oxidation exist: (I) Carbonyl + H a O + pyridine‐enzyme ← carboxylate + reduced pyridine‐enzyme. This type of oxidation is practically irreversible and consequently liberates a large amount of free energy. The normal redoxpotential of this system is extraordinarily low, i.e. carbonyl is a very strong reducing agent. (2) Carbonyl + phosphate + pyridine‐enzyme ← carboxylphosphate + reduced pyridine‐enzyme. This type of oxidation is reversible and the change in free energy accordingly very small, which means that the normal redoxpotential of the system: carbonyl + phosphate ← carboxylphosphate + 2←+ 2H + is very close to that of the system: pyridine‐enzyme ← reduced pyridine‐enzyme + 2←+ H + . Thus replacement of water by phosphate in the carbonyl oxidation eliminates a great fall in free energy by transforming the labile carbonyl into an equally labile acid anhydride, carboxylphosphate. The degradation of the polyalcohol structure of the sugar acid (glyceric acid) to the α‐keto acid structure of pyruvic acid releases a considerable amount of energy. Moreover, in this case the energy is directed and preserved by means of a phosphorylation. I am indebted to Dr D. M. Needham (Cambridge) for her generous help in preparing the manuscript for publication and to Prof. C. F. Cori, Dr G. T. Cori and Mr S. P. Colowick for their valuable and helpful suggestions.