Simon M, Hong J S
J Bacteriol. 1983 Jan;153(1):558-61. doi: 10.1128/jb.153.1.558-561.1983.
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.
发现了一些突变，这些突变能使大肠杆菌K-12在缺乏胱硫醚酶的情况下形成同型半胱氨酸。突变菌株中同型半胱氨酸的形成需要胱硫醚γ-合成酶（metB基因产物），但绕过了正常的中间产物胱硫醚。得出的结论是，胱硫醚γ-合成酶直接催化从O-琥珀酰高丝氨酸和一种尚未确定的硫供体形成同型半胱氨酸。该突变显然导致了这种硫供体的形成，并被命名为metQ。metQ基因的表达受分解代谢物阻遏。
