Direct homocysteine biosynthesis from O-succinylhomoserine in Escherichia coli: an alternate pathway that bypasses cystathionine.

M Simon, J S Hong

Index: J. Bacteriol. 153(1) , 558-61, (1983)

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Abstract

Mutations were found which enable Escherichia coli K-12 to form homocysteine in the absence of cystathionase. The formation of homocysteine in the mutant strains required cystathionine gamma-synthetase, the metB gene product, but bypassed the normal intermediate cystathionine. It is concluded that cystathionine gamma-synthetase catalyzes the formation of homocysteine directly from O-succinylhomoserine and an as-yet-unidentified sulfur donor. The mutation apparently causes the formation of this sulfur donor and has been named metQ. The expression of the metQ gene is under catabolite repression.