Veenstra J A
Laboratoire de Neuroendocrinologie, Université Bordeaux I, Talence, France.
Arch Insect Biochem Physiol. 2000 Feb;43(2):49-63. doi: 10.1002/(SICI)1520-6327(200002)43:2<49::AID-ARCH1>3.0.CO;2-M.
Regulatory peptides are synthesized as part of larger precursors that are subsequently processed into the active substances. After cleavage of the signal peptide, further proteolytic processing occurs predominantly at basic amino acid residues. Rules have been proposed in order to predict which putative proteolytic processing sites are actually used, but these rules have been established for vertebrate peptide precursors and it is unclear whether they are also valid for insects. The aim of this paper is to establish the validity of these rules to predict proteolytic cleavage sites at basic amino acids in insect neuropeptide precursors. Rules describing the cleavage of mono- and dibasic potential processing sites in insect neuropeptide precursors are summarized below. Lys-Arg pairs not followed by an aliphatic or basic amino acid residue are virtually always cleaved in insect regulatory peptide precursors, but cleavages of Lys-Arg pairs followed by either an aliphatic or a basic amino acid residue are ambiguous, as is processing at Arg-Arg pairs. Processing at Arg-Lys pairs has so far not been demonstrated in insects and processing at Lys-Lys pairs appears very rare. Processing at single Arg residues occurs only when there is a basic amino acid residue in position -4, -6, or -8, usually an Arg, but Lys or His residues work also. Although the current number of such sites is too limited to draw definitive conclusions, it seems plausible that cleavage at these sites is inhibited by the presence of aliphatic residues in the +1 position. However, cleavage at single Arg residues is ambiguous. When several potential cleavage sites overlap the one most easily cleaved appears to be processed. It cannot be excluded that some of the rules formulated here will prove less than universal, as only a limited number of cleavage sites have so far been identified. It is likely that, as in vertebrates, ambiguous processing sites exist to allow differential cleavage of the same precursor by different convertases and it seems possible that the precursors of allatostatins and PBAN are differentially cleaved in different cell types. Arch. Insect Biochem. Physiol. 43:49-63, 2000.
调节肽作为较大前体的一部分被合成，随后被加工成活性物质。信号肽裂解后，进一步的蛋白水解加工主要发生在碱性氨基酸残基处。已经提出了一些规则来预测哪些假定的蛋白水解加工位点会被实际利用，但这些规则是针对脊椎动物肽前体建立的，目前尚不清楚它们对昆虫是否也有效。本文的目的是确定这些规则对预测昆虫神经肽前体中碱性氨基酸处蛋白水解裂解位点的有效性。下面总结了描述昆虫神经肽前体中单碱性和双碱性潜在加工位点裂解的规则。在昆虫调节肽前体中，后面不跟着脂肪族或碱性氨基酸残基的Lys-Arg对几乎总是会被裂解，但后面跟着脂肪族或碱性氨基酸残基的Lys-Arg对的裂解情况不明确，Arg-Arg对的加工也是如此。到目前为止，昆虫中尚未证实存在Arg-Lys对的加工，而Lys-Lys对的加工似乎非常罕见。只有当-4、-6或-8位存在碱性氨基酸残基（通常是Arg，但Lys或His残基也可以）时，才会发生单个Arg残基处的加工。尽管目前此类位点的数量有限，无法得出明确结论，但在+1位存在脂肪族残基似乎会抑制这些位点的裂解，这似乎是合理的。然而，单个Arg残基处的裂解情况不明确。当几个潜在裂解位点重叠时，最容易裂解的那个似乎会被加工。由于目前仅鉴定出有限数量的裂解位点，因此不能排除这里制定的一些规则并非普遍适用的可能性。与脊椎动物一样，可能存在不明确的加工位点，以便不同的转化酶对同一前体进行差异裂解，而且保幼激素抑制肽和PBAN的前体在不同细胞类型中可能会被差异裂解。《昆虫生物化学与生理学档案》43:49 - 63，2000年。
