Activities | Families | Sequences | Fold types | References | Help
B6db references: 20061037

type Journal Article
authors Clausen, T.; Wahl, M. C.; Messerschmidt, A.; Huber, R.; Fuhrmann, J. C.; Laber, B.; Streber, W.; Steegborn, C.
title Cloning, purification and characterisation of cystathionine gamma- synthase from Nicotiana tabacum
journal Biol Chem
ui 20061037
year (1999)
volume 380
number 10
pages 1237-42.
keywords Amino Acid Sequence
abstract Cystathionine gamma-synthase, the enzyme catalysing the first reaction specific for methionine biosynthesis, has been cloned from Nicotiana tabacum, overexpressed in Escherichia coli and purified to homogeneity. The recombinant cystathionine gamma-synthase catalyses the pyridoxal 5'- phosphate dependent formation of L-cystathionine from L-homoserine phosphate and L-cysteine with apparent Km-values of 7.1+/-3.1 mM and of 0.23+/-0.07 mM, respectively. The enzyme was irreversibly inhibited by DL-propargylglycine (Ki = 18 microM, k(inact) = 0.56 min(-1)), while the homoserine phosphate analogues 3-(phosphonomethyl)pyridine-2- carboxylic acid, 4-(phosphonomethyl)pyridine-2-carboxylic acid, Z-3-(2- phosphonoethen-1-yl)pyridine-2-carboxylic acid, and DL-E-2-amino-5- phosphono-3-pentenoic acid acted as reversible competitive inhibitors with Ki values of 0.20, 0.30, 0.45, and 0.027 mM, respectively. In combination these results suggest a ping-pong mechanism for the cystathionine gamma-synthase reaction, with homoserine phosphate binding to the enzyme first. Large single crystals of cystathionine gamma-synthase diffracting to beyond 2.7 A resolution were obtained by the sitting drop vapour diffusion method. The crystals belong to the orthorhombic space group P2(1)2(1)2(1) with unit cell constants a = 120.0 A, b = 129.5 A, c = 309.8 A, corresponding to two tetramers per asymmetric unit.
last changed 2003/03/17 15:08

B6db references