Takeda O, Miura Y, Mitta M, Matsushita H, Kato I, Abe Y, Yokosawa H, Ishii S
Biotechnology Research Laboratories, Takara Shuzo Co., Ltd., Otsu.
J Biochem. 1994 Sep;116(3):541-6. doi: 10.1093/oxfordjournals.jbchem.a124559.
Recently, asparaginyl endopeptidase was purified to homogeneity from jack bean (Canavalia ensiformis) seeds, and its NH2-terminal amino acid sequence was determined for 25 residues [Abe, Y. et al. (1993) J. Biol. Chem. 268, 3525-3529]. On the basis of this sequence information, we searched for seed cDNAs encoding this enzyme. Seven clones were obtained and sequenced. By combining four of them, we obtained a cDNA for a precursor of the enzyme containing the reported NH2-terminal sequence. The other three clones seemed to be for precursors of its isozymes. When the deduced amino acid sequences of these enzyme precursors were compared with those in the GeneBank, EMBL, and NBRF databases, only one protein was found with a homologous sequence. It was a precursor of hemoglobinase from a blood fluke (Schistosoma mansoni). Significant homology was observed only in the range of sequence for the mature form. Although hemoglobinase and asparaginyl endopeptidase behave as cysteine proteinases, their protein natures are distinct from either papain-type proteinases or clostripain. Various plant seeds have been reported to contain asparaginyl endopeptidases. This may be the first report, however, that deals with the primary structure of such a proteinase.
最近，天冬酰胺基内肽酶从刀豆（Canavalia ensiformis）种子中被纯化至同质状态，并且测定了其25个残基的NH2末端氨基酸序列[Abe, Y.等人（1993年）《生物化学杂志》268, 3525 - 3529]。基于该序列信息，我们搜索了编码此酶的种子cDNA。获得了七个克隆并进行了测序。通过将其中四个组合起来，我们得到了一种该酶前体的cDNA，其包含已报道的NH2末端序列。另外三个克隆似乎是其同工酶前体的。当将这些酶前体推导的氨基酸序列与基因库、EMBL和NBRF数据库中的序列进行比较时，仅发现一种具有同源序列的蛋白质。它是一种来自血吸虫（曼氏血吸虫）的血红蛋白酶前体。仅在成熟形式的序列范围内观察到显著的同源性。尽管血红蛋白酶和天冬酰胺基内肽酶表现为半胱氨酸蛋白酶，但它们的蛋白质性质不同于木瓜蛋白酶型蛋白酶或梭菌蛋白酶。据报道，各种植物种子都含有天冬酰胺基内肽酶。然而，这可能是第一篇涉及此类蛋白酶一级结构的报道。
