Newman E B, Adley T, Fraser J, Potter R, Kapoor V
Can J Microbiol. 1976 Jul;22(7):922-8. doi: 10.1139/m76-133.
The amino acid L-leucine serves as a good auxiliary nitrogen source for Escherichia coli K12, and in so doing is converted to alpha-ketoisocaproic acid which is excreted into the medium. L-Leucine does not serve as sole nitrogen source. Cells incubated with L-leucine as sole nitrogen source do not grow, although they do metabolize leucine, and accumulate ketoisocaproic acid in the medium. Where glycine is the only other nitrogen source, the presence of L-leucine greatly increases the growth rate even at concentrations so low that its contribution as nitrogen donor is unlikely to be important.
氨基酸L-亮氨酸是大肠杆菌K12良好的辅助氮源，在此过程中它被转化为α-酮异己酸，后者被分泌到培养基中。L-亮氨酸不能作为唯一的氮源。以L-亮氨酸作为唯一氮源培养的细胞虽能代谢亮氨酸，但不会生长，且培养基中会积累酮异己酸。在只有甘氨酸可作为其他氮源的情况下，即使L-亮氨酸的浓度很低，以至于其作为氮供体的作用可能并不重要，但它的存在仍能显著提高生长速率。
