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B6db references: 98153172

type Journal Article
authors van Ophem, P. W.; Erickson, S. D.; Martinez del Pozo, A.; Haller, I.; Chait, B. T.; Yoshimura, T.; Soda, K.; Ringe, D.; Petsko, G.; Manning, J. M.
title Substrate inhibition of D-amino acid transaminase and protection by salts and by reduced nicotinamide adenine dinucleotide: isolation and initial characterization of a pyridoxo intermediate related to inactivation
journal Biochemistry
ui 98153172
year (1998)
volume 37
number 9
pages 2879-88.
keywords Alanine/pharmacology
abstract D-Amino acid transaminase, a pyridoxal phosphate (PLP) enzyme, is inactivated by its natural substrate, D-alanine, concomitant with its alpha-decarboxylation [Martinez del Pozo, A., Yoshimura, T., Bhatia, M. B., Futaki, S., Manning, J. M., Ringe, D., and Soda, K. (1992) Biochemistry 31, 6018-6023; Bhatia, M. B., Martinez del Pozo, A., Ringe, D., Yoshimura, T., Soda, K., and Manning, J. M. (1993) J. Biol. Chem. 268, 17687-17694]. beta-Decarboxylation of d-aspartate to d- alanine leads also to this inactivation [Jones, W. M., van Ophem, P. W., Pospischil, M. A., Ringe, D., Petsko, G., Soda, K., and Manning, J. M. (1996) Protein Sci. 5, 2545-2551]. Using a high-performance liquid chromatography-based method for the determination of pyridoxo cofactors, we detected a new intermediate closely related to the inactivation by d-alanine; its formation occurred at the same rate as the inactivation and upon reactivation it reverted to PLP. Conditions were found under which it was characterized by ultraviolet-visible spectral analysis and mass spectroscopy; it is a pyridoxamine phosphate- like compound with a C2 fragment derived from the substrate attached to the C'-4 of the pyridinium ring and it has a molecular mass of 306 consistent with this structure. In the presence of d-serine, slow accumulation of a quinonoid intermediate is also related to inactivation. The inactivation can be prevented by salts, which possibly stabilize the protonated aldimine coenzyme complex. The reduced cofactor, nicotinamide adenine dinucleotide, prevents D- aspartate-induced inactivation. Both of these events also are related to formation of the novel intermediate.
last changed 2002/11/04 17:41

B6db references