期刊
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
卷 433, 期 1, 页码 279-287出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2004.09.037
关键词
reaction specificity; pyridoxal phosphate; dialkylglycine decarboxylase; alanine racemase
资金
- NIGMS NIH HHS [GM54779] Funding Source: Medline
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R56GM054779, R01GM054779] Funding Source: NIH RePORTER
Pyridoxal phosphate enzymes catalyze a wide variety of reaction types on amines and amino acids, generally by stabilizing carbanionic intermediates. This makes them very useful in cellular metabolism, but it also creates problems in controlling the reaction pathway that a given enzyme follows, i.e., in controlling reaction specificity. Stereoelectronic effects have been proposed to play a major role in determining the bond to Calpha that gets broken in the external aldimine intermediate that is common to all PLP enzymes. Here, we discuss our work on dialkylglycine decarboxylase aimed at providing direct evidence for stereoelectronic control of external aldimine reactivity. Once a bond to Calpha has been broken to form the carbanionic intermediate, enzymes must also carefully control the fate of this reactive species. Our studies with alanine racemase suggest that the enzyme selectively destabilizes the carbanionic quinonoid intermediate to promote higher racemization specificity by avoiding transamination side reactions. (C) 2004 Elsevier Inc. All rights reserved.
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