Glutamate decarboxylase side reactions catalyzed by the enzyme

Content Provider	Scilit
Author	Choi, Soo Young Churchich, Jorge E.
Copyright Year	1986
Description	Journal: Journal of Biological Inorganic Chemistry A homogeneous glutamate decarboxylase isolated from pig brain contains 0.8 mol of tightly bound pyridoxal 5‐phosphate/enzyme dimer. Upon addition of exogenous pyridoxal 5‐phosphate (pyridoxal‐5‐P), the enzyme acquires maximum catalytic activity. Preincubation of the enzyme with l‐glutamate (10 mM) brings about changes in the absorption spectrum of bound pyridoxal‐5‐P with the concomitant formation of succinic semialdehyde. However, the rate of this slow secondary reaction, i.e. decarboxylative transamination, is $10^{−4}$ times the rate of normal decarboxylation. It is postulated that under physiological conditions enzymatically inactive species of glutamate decarboxylase, generated by the process of decarboxylative transamination, are reconstituted by pyridoxal‐5‐P produced by the cytosolic enzymes pyridoxal kinase and pyridoxine‐5‐P oxidase. The catalytic activity of resolved glutamate decarboxylase is recovered by preincubation with phospho‐pyridoxyl‐ethanolamine phosphate. The experimental evidence is consistent with the interpretation that the resolved enzyme binds the P‐pyridoxyl analog, reduces the stability of the covalent bond of the phospho‐pyridoxyl moiety, and catalyzes the formation of pyridoxal‐5‐P.
Ending Page	520
Starting Page	515
ISSN	2573508X
e-ISSN	14321327
DOI	10.1111/j.1432-1033.1986.tb10069.x
Journal	Journal of Biological Inorganic Chemistry
Issue Number	3
Volume Number	160
Language	English
Publisher	Wiley-Blackwell
Publisher Date	1986-11-01
Access Restriction	Open
Subject Keyword	Journal: Journal of Biological Inorganic Chemistry Glutamate Decarboxylase
Content Type	Text
Resource Type	Article
Subject	Biochemistry Inorganic Chemistry