Garside C S, Hayes T K, Tobe S S
Department of Zoology, University of Toronto, ON, Canada.
Peptides. 1997;18(1):17-25. doi: 10.1016/s0196-9781(96)00244-6.
Incubation of Dip-AST 7 (APSGAQRLYGFGLa) or Dip-AST 9 (GDGRLYAFGLa) (5 microM) with hemolymph for 30 min results in cleavage by a putative endopeptidase, yielding the C-terminal hexapeptide. This metabolic product is subsequently cleaved by an amastatin-sensitive aminopeptidase to yield the the C-terminal pentapeptide, as treatment with the competitive aminoexopeptidase inhibitor, amastatin, results in a significant accumulation of the C-terminal hexapeptide. Interestingly, Dip-AST 5 (DRLYSFGLa) (6 microM), which in common with Dip-AST 7 and 9 possesses Arg-Leu-Tyr, is not rapidly cleaved. However, [3H-Tyr]Dip-AST 5 at physiological concentrations (4 nM), appears to be cleaved by the same enzymes that cleave Dip-AST 7 and 9, albeit at a reduced rate. Incubation of other members of the Dip-allatostatin family with hemolymph also results in cleavage of the peptides, suggesting that there are a variety of endo- and/or exopeptidases present in the hemolymph of D. punctata.
将 Dip-AST 7（APSGAQRLYGFGLa）或 Dip-AST 9（GDGRLYAFGLa）（5 微摩尔）与血淋巴孵育 30 分钟，会被一种假定的内肽酶切割，产生 C 端六肽。这种代谢产物随后会被一种氨肽酶抑制剂敏感的氨肽酶切割，产生 C 端五肽，因为用竞争性氨肽酶抑制剂氨肽素处理会导致 C 端六肽大量积累。有趣的是，与 Dip-AST 7 和 9 一样含有 Arg-Leu-Tyr 的 Dip-AST 5（DRLYSFGLa）（6 微摩尔）不会被快速切割。然而，生理浓度（4 纳摩尔）的[3H-酪氨酸]Dip-AST 5 似乎会被切割 Dip-AST 7 和 9 的相同酶切割，尽管切割速率较低。将 Dip-咽侧体抑制素家族的其他成员与血淋巴孵育也会导致肽段被切割，这表明在斑点按蚊的血淋巴中存在多种内切酶和/或外切酶。
