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B6db references: 90105412

type Journal Article
authors Martinez del Pozo, A.; Pospischil, M. A.; Ueno, H.; Manning, J. M.; Tanizawa, K.; Nishimura, K.; Soda, K.; Ringe, D.; Stoddard, B.; Petsko, G. A.
title Effects of D-serine on bacterial D-amino acid transaminase: accumulation of an intermediate and inactivation of the enzyme
journal Biochemistry
ui 90105412
year (1989)
volume 28
number 22
pages 8798-803.
keywords Circular Dichroism
abstract Incubation of pure bacterial D-amino acid transaminase with D-serine or erythro-beta-hydroxy-DL-aspartic acid, which are relatively poor substrates, leads to generation of a new absorbance band at 493 nm that is probably the quinonoid intermediate. The 420-nm absorbance band (due to the pyridoxal phosphate coenzyme) decreases, and the 338-nm absorbance band (due to the pyridoxamine phosphate or some other form of the coenzyme) increases. A negative Cotton effect at 493 nm in the circular dichroism spectra is also generated. Closely related D amino acids do not lead to generation of this new absorption band, which has a half-life of the order of several hours. Treatment of the enzyme with the good substrate D-alanine leads to a small but detectable amount of the same absorbance band. D-Serine but not erythro-beta- hydroxyaspartate leads to inactivation of D-amino acid transaminase, and D-alanine affords partial protection. The results indicate that D- serine is a unique type of inhibitor in which the initial steps of the half-reaction of transamination are so slow that a quinonoid intermediate with a 493-nm absorption band accumulates. A derivative formed from this intermediate inactivates the enzyme.
last changed 2002/11/04 17:41

B6db references