Brown E A, D'Ari R, Newman E B
Department of Biology, Concordia University, Montreal, Canada.
J Gen Microbiol. 1990 Jun;136(6):1017-23. doi: 10.1099/00221287-136-6-1017.
While wild-type Escherichia coli K12 cannot grow with L-serine as carbon source, two types of mutants with altered methionine metabolism can. The first type, metJ mutants, in which the methionine biosynthetic enzymes are expressed constitutively, are able to grow with L-serine as carbon source. Furthermore, a plasmid carrying the metC gene confers ability to grow on L-serine. These observations suggest that in these mutants, L-serine deamination may be a result of a side-reaction of the metC gene product, cystathionine beta-lyase. The second type is exemplified by two newly isolated strains carrying mutations mapping between 89.6 and 90 min. These mutants use L-serine as carbon source, and also require methionine for growth with glucose at 37 degrees C and above. The phenotypes of the new mutants resemble those of both met and his constitutive mutants in some respects, but have been differentiated from both of them.
野生型大肠杆菌K12不能以L-丝氨酸作为碳源生长，但两种甲硫氨酸代谢改变的突变体可以。第一种类型是metJ突变体，其中甲硫氨酸生物合成酶组成型表达，能够以L-丝氨酸作为碳源生长。此外，携带metC基因的质粒赋予了在L-丝氨酸上生长的能力。这些观察结果表明，在这些突变体中，L-丝氨酸脱氨可能是metC基因产物胱硫醚β-裂合酶副反应的结果。第二种类型以两个新分离的菌株为例，它们携带的突变位于89.6至90分钟之间。这些突变体以L-丝氨酸作为碳源，并且在37℃及以上温度下以葡萄糖生长时也需要甲硫氨酸。新突变体的表型在某些方面类似于met和his组成型突变体，但已与它们两者区分开来。
