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B6db references: 24777760

type Journal Article
authors Yafuso JT1, Negi VS, Bingham JP, Borthakur D.
title An O-Acetylserine (thiol) Lyase from Leucaena leucocephala Is a Cysteine Synthase But Not a Mimosine Synthase
journal Appl Microbiol Biotechnol.
Activity 2.5.1.47
Family 2.5.1.47
sel selected
ui 24777760
year (2014)
volume 173
number 5
pages 1157-68
 
abstract In plants, the final step of cysteine formation is catalyzed by O-acetylserine (thiol) lyase (OAS-TL). The purpose of this study was to isolate and characterize an OAS-TL from the tree legume Leucaena leucocephala (leucaena). Leucaena contains a toxic, nonprotein amino acid, mimosine, which is also formed by an OAS-TL, and characterization of this enzyme is essential for developing a mimosine-free leucaena for its use as a protein-rich fodder. The cDNA for a cytosolic leucaena OAS-TL isoform was obtained through interspecies suppression subtractive hybridization. A 40-kDa recombinant protein was purified from Escherichia coli and used in enzyme activity assays where it was found to synthesize only cysteine. The enzyme followed Michaelis-Menten kinetics, and the K m was calculated to be 1,850  414 μM sulfide and the V max was 200.6  19.92 μM cysteine min(-1). The N-terminal affinity His-tag was cleaved from the recombinant OAS-TL to eliminate its possible interference in binding with the substrate, 3-hydroxy-4-pyridone, for mimosine formation. The His-tag-cleaved OAS-TL was again observed to catalyze the formation of cysteine but not mimosine. Thus, the cytosolic OAS-TL from leucaena used in this study is specific for only cysteine synthesis and is different from previously reported OAS-TLs that also function as β-substituted alanine synthases.
last changed 2014/07/09 13:12

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