McHugh G L, Miller C G
J Bacteriol. 1974 Oct;120(1):364-71. doi: 10.1128/jb.120.1.364-371.1974.
The proline requirement of Salmonella typhimurium strain proB25 can be satisfied by either of the peptides Leu-Pro or Gly-Pro-Ala. A mutant derivative of strain proB25 isolated by penicillin selection in medium containing Leu-Pro as proline source fails to use either Leu-Pro or Gly-Pro-Ala as a source of proline. This strain is a double mutant that lacks two aminoacyl-proline-specific peptidases. One of these enzymes (peptidase Q) catalyzes the rapid hydrolysis of Leu-Pro but does not hydrolyze Gly-Pro-Ala or poly-l-proline. Mutations at a site (pepQ) near metE lead to loss of this activity. The other peptidase (peptidase P) catalyzes the hydrolysis of Gly-Pro-Ala and poly-l-proline but is only weakly active with Leu-Pro as substrate. This enzyme is similar to aminopeptidase P previously described in Escherichia coli (16). Mutations at a locus (pepP) near serA lead to loss of this enzyme.
鼠伤寒沙门氏菌proB25菌株对脯氨酸的需求可以通过Leu-Pro或Gly-Pro-Ala这两种肽中的任何一种来满足。在以Leu-Pro作为脯氨酸来源的培养基中通过青霉素筛选分离出的proB25菌株的突变衍生物，无法将Leu-Pro或Gly-Pro-Ala用作脯氨酸来源。该菌株是一个双突变体，缺乏两种氨酰基脯氨酸特异性肽酶。其中一种酶（肽酶Q）催化Leu-Pro的快速水解，但不水解Gly-Pro-Ala或聚-L-脯氨酸。在metE附近的一个位点（pepQ）发生突变会导致这种活性丧失。另一种肽酶（肽酶P）催化Gly-Pro-Ala和聚-L-脯氨酸的水解，但以Leu-Pro作为底物时活性较弱。这种酶类似于先前在大肠杆菌中描述的氨肽酶P（16）。在serA附近的一个基因座（pepP）发生突变会导致这种酶的丧失。
