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B6db references: 12269813

type Journal Article
authors Kielkopf, C. L.; Burley, S. K.
title X-ray structures of threonine aldolase complexes: Structural basis of substrate recognition
journal Biochemistry
sel selected
ui 12269813
year (2002)
volume 41
number 39
pages 11711-20
abstract L-Threonine acetaldehyde-lyase (threonine aldolase, TA) is a pyridoxal- 5'-phosphate-dependent (PLP) enzyme that catalyzes conversion of L- threonine or L-allo-threonine to glycine and acetaldehyde in a secondary glycine biosynthetic pathway. X-ray structures of Thermatoga maritima TA have been determined as the apo-enzyme at 1.8 A resolution and bound to substrate L-allo-threonine and product glycine at 1.9 and 2.0 A resolution, respectively. Despite low pairwise sequence identities, TA is a member of aspartate aminotransferase (AATase) fold family of PLP enzymes. The enzyme forms a 222 homotetramer with the PLP cofactor bound via a Schiff-base linkage to Lys199 within a domain interface. The structure reveals bound calcium and chloride ions that appear to contribute to catalysis and oligomerization, respectively. Although L-threonine and L-allo-threonine are substrates for T. maritima TA, enzymatic assays revealed a strong preference for L-allo- threonine. Structures of the external aldimines with substrate/product reveal a pair of histidines that may provide flexibility in substrate recognition. Variation in the threonine binding pocket may explain preferences for L-allo-threonine versus L-threonine among TA family members.
last changed 2009/06/19 13:24

B6db references