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B6db references: 90216689

type Journal Article
authors Bhattacharjee, M. K.; Snell, E. E.
title Pyridoxal 5'-phosphate-dependent histidine decarboxylase. Mechanism of inactivation by alpha-fluoromethylhistidine
journal J Biol Chem
ui 90216689
year (1990)
volume 265
number 12
pages 6664-8.
keywords Carboxy-Lyases/*antagonists & inhibitors
abstract Mechanism-based inactivation of pyridoxal phosphate-dependent histidine decarboxylase by (S)-alpha-(fluoromethyl)histidine was studied. The molar ratio of inactivator to enzyme subunit required for complete inactivation increased from 1.63 at 10 degrees C to 3.00 at 37 degrees C. Two inactivation products were isolated by chromatographic fractionation of the reaction mixture and identified by NMR spectroscopy as 1-(4-imidazolyl)-3(5'-P-pyridoxylidene) acetone (I), the adduct formed between pyridoxal phosphate and inactivator, and 1-(4- imidazolyl) acetone (II), an intermediate compound formed during inactivation. Formation of these two products supports a previously proposed mechanism of inactivation (Hayashi, H., Tanase, S., and Snell, E. E. (1986) J. Biol. Chem. 261, 11003-11009), with minor modifications. A precursor of I was linked covalently to the enzyme by NaBH4 reduction if the reaction was carried out immediately after inactivation, before development of the 403 nm peak of I. A mutant histidine decarboxylase (S322A) in which Ser-322 was changed to Ala was also inactivated by alpha-fluoromethylhistidine demonstrating that Ser- 322 is not essential for inactivation even though it is close to the active site and is derivatized by borohydride reduction of the inactivated wild-type enzyme. Following inactivation, both the wild- type and the S322A mutant enzyme could be partially reactivated by prolonged dialysis against buffer.
last changed 2002/11/12 16:17

B6db references