|
type |
Journal Article |
authors |
Yi H, Juergens M, Jez JM |
title |
Structure of soybean β-cyanoalanine synthase and the molecular basis for cyanide detoxification in plants |
journal |
Plant Cell |
Activity |
4.4.1.9 |
Family |
4.4.1.9.a |
sel |
selected |
ui |
22739827 |
year |
(2012) |
volume |
39 |
number |
10 |
pages |
2696-706 |
| |
keywords |
doi: 10.1105/tpc.112.098954 |
abstract |
Plants produce cyanide (CN-) during ethylene biosynthesis in the mitochondria and require β-cyanoalanine synthase (CAS) for CN- detoxification. Recent studies show that CAS is a member of the β-substituted alanine synthase (BSAS) family, which also includes the Cys biosynthesis enzyme O-acetylserine sulfhydrylase (OASS), but how the BSAS evolved distinct metabolic functions is not understood. Here we show that soybean (Glycine max) CAS and OASS form α-aminoacrylate reaction intermediates from Cys and O-acetylserine, respectively. To understand the molecular evolution of CAS and OASS in the BSAS enzyme family, the crystal structures of Gm-CAS and the Gm-CAS K95A mutant with a linked pyridoxal phosphate (PLP)-Cys molecule in the active site were determined. These structures establish a common fold for the plant BSAS family and reveal a substrate-induced conformational change that encloses the active site for catalysis. Comparison of CAS and OASS identified residues that covary in the PLP binding site. The Gm-OASS T81M, S181M, and T185S mutants altered the ratio of OASS:CAS activity but did not convert substrate preference to that of a CAS. Generation of a triple mutant Gm-OASS successfully switched reaction chemistry to that of a CAS. This study provides new molecular insight into the evolution of diverse enzyme functions across the BSAS family in plants. |
last changed |
2018/05/03 12:42 |
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