期刊
CURRENT OPINION IN CHEMICAL BIOLOGY
卷 13, 期 4, 页码 475-483出版社
CURRENT BIOLOGY LTD
DOI: 10.1016/j.cbpa.2009.06.023
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资金
- NIH [GM39754]
- Ministerio de Educacion y Ciencia
- European Regional Development Fund (ERDF) [CTQ2004-06594]
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM039754, R29GM039754] Funding Source: NIH RePORTER
Studies of nonenzymatic electrophilic catalysis of carbon deprotonation of glycine show that pyridoxal 5'-phosphate (PLP) strongly enhances the carbon acidity of alpha-amino acids, but that this is not the overriding mechanistic imperative for cofactor catalysis. Although the fully protonated PLP-glycine iminium ion adduct exhibits an extraordinary low alpha-imino carbon acidity (pK(a) = 6), the more weakly acidic zwitterionic iminium ion adduct (pK(a) = 17) is selected for use in enzymatic reactions. The similar alpha-imino carbon acidities of the iminium ion adducts of glycine with 5'-deoxypyridoxal and with phenylglyoxylate show that the cofactor pyridine nitrogen plays a relatively minor role in carbanion stabilization. The 5'-phosphodianion group of PLP likely plays an important role in catalysis by providing up to 12 kcal/mol of binding energy that may be utilized for transition state stabilization.
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