234 PYRIDOXINE AND RELATED COMPOUNDS 



IV. Biochemical Systems 



W. W. UMBREIT 



A. GENERAL 



Pyridoxine, like other vitamins, functions in the form of a coenzyme. 

 This coenzyme, which has been variously termed codecarboxylase, cotrans- 

 aminase, etc., is the 5-phosphate of pyridoxal. The various members of the 

 vitamin Be group — ^pyridoxine, pyridoxal, pyridoxamine, and their respec- 

 tive phosphates — owe their vitamin activity to the ability of the organism 

 to convert them into the enzymatically active form, pyridoxal-5-phosphate. 

 Recently several papers have appeared which further extend our informa- 

 tion. In addition to chemical studies on structure,^ the crystalline pyridoxal 

 and pyridoxamine phosphates^^ have been prepared. 



Pyridoxine is concerned with the activity of a wide variety of enzyme 

 systems. These catalyze reactions which have apparently very little in 

 common, except that all are characterized by action of one sort or another 

 upon amino acids. The known enzyme systems are listed in the following 

 paragraphs. 



B. AMINO ACID DECARBOXYLASES 



The properties of the amino acid decarboxylases have been so well de- 

 scribed in reviews^"^ that no great detail is necessary here. Their distribu- 

 tion and their relation to pyridoxal phosphate is given in Table I, from 

 which it is evident that they occur predominantly in bacteria and to a lesser 

 extent in other organisms. However, even among the bacteria, their dis- 

 tribution varies greatly from one strain to another. Their physiological 

 significance is at present unknown. The enzymes decarboxylating aspartic 

 acid to jS-alanine are probably of nutritional value,^^ • "** and those decarboxy- 



1 M. Viscontini, C. Ebnother, and P. Karrer, Helv. Chini. Acta 34, 1834, 2198, 2199, 

 2438 (1951); M. Viscontini and E. G. Bonetti, Helv. Chim. Acta 34, 2435 (1951); 

 J. Baddiley and A. P. Mathias, J. Chem. Soc. 1952, 2583. 



1" E. A. Peterson, H. A. Sober, and A. Meister, J. Am. Chem. Soc. 74, 570 (1952). 



2 H. Blaschko, Advances in Enzymol. 5, 67 (1945). 

 2a E. F. Gale, Advances in Enzymol. 6, 1 (1946). 



3 I. C. Gunsalus, Federation Proc. 9, 556 (1950). 



* O. Schales, Advances in Enzymol. 7, 513 (1947). 



^ O. Schales, in The Enzymes, Vol. 2, Part 1, p. 216. Academic Press, New York, 



1951. 

 ^ E. Werle, Z. Vitamin-Hormon-u. Fermentforsch. 1, 504 (1947). 

 7 E. F. Gale, Biochem. J. 34, 392 (1940). 

 »E. S. Taylor and E. F. Gale, Biochem. J. 39, 52 (1945). 

 9 H. M. R. Epps, Biochem. J. 39, 42 (1945). 



i» S. R. Mardasheu and R. N. Etingof, Biokhimia 13, 469 (1948) [C. A. 43, .3065 

 (1949)1. 



