Takahashi K, Inoue H, Sakai K, Kohama T, Kitahara S, Takishima K, Tanji M, Athauda S B, Takahashi T, Akanuma H
Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
J Biol Chem. 1991 Oct 15;266(29):19480-3.
The complete amino acid sequence of the acid proteinase A, a non-pepsin type acid proteinase from the fungus Aspergillus niger var. macrosporus, was determined by protein sequencing. The enzyme was first dissociated at pH 8.5 into a light (L) chain and a heavy (H) chain, and the L chain was sequenced completely. Further sequencing was performed with the reduced and pyridylethylated or aminoethylated derivative of the whole protein, using peptides obtained by digestions with Staphylococcus aureus V8 protease, trypsin, chymotrypsin, and lysylendopeptidase. The location of the two disulfide bonds was determined by analysis of cystine-containing peptides obtained from a chymotryptic digest of the unmodified protein. These results established that the protein consists of a 39-residue L chain and a 173-residue H chain that associate noncovalently to form the native enzyme of 212 residues (Mr 22,265). This is, to our knowledge, the first time that such a protein with a rather short peptide chain associated noncovalently has been found. No sequence homology is found with other acid or aspartic proteinases, except for Scytalidium lignicolum acid proteinase B, an enzyme unrelated to pepsin by sequence, which has about 50% identity with the present enzyme. These two enzymes, however, are remarkably different from each other in some structural features.
黑曲霉大孢子变种来源的一种非胃蛋白酶型酸性蛋白酶A的完整氨基酸序列通过蛋白质测序得以确定。该酶首先在pH 8.5条件下解离成轻链（L链）和重链（H链），并对L链进行了完全测序。随后，使用金黄色葡萄球菌V8蛋白酶、胰蛋白酶、糜蛋白酶和赖氨酰内肽酶消化得到的肽段，对整个蛋白质的还原及吡啶基乙基化或氨乙基化衍生物进行进一步测序。通过分析未修饰蛋白质的糜蛋白酶消化产物中含胱氨酸的肽段，确定了两条二硫键的位置。这些结果表明，该蛋白质由一条39个残基的L链和一条173个残基的H链组成，它们通过非共价结合形成了含有212个残基（Mr 22,265）的天然酶。据我们所知，这是首次发现具有相当短肽链且通过非共价结合的此类蛋白质。除了木生弯孢霉酸性蛋白酶B（一种与胃蛋白酶在序列上无关的酶，与本酶具有约50%的同一性）外，未发现与其他酸性或天冬氨酸蛋白酶有序列同源性。然而，这两种酶在某些结构特征上彼此显著不同。
