Department of Agricultural Chemistry, Kyushu University, Fukuoka 812, Japan.
Appl Environ Microbiol. 1986 Nov;52(5):1068-73. doi: 10.1128/aem.52.5.1068-1073.1986.
Mutational experiments were carried out to decrease the protease productivity of Aspergillus ficum IFO 4320 by using N-methyl-N'-nitro-N-nitrosoguanidine. A protease-negative mutant, M-33, exhibited higher alpha-amylaseactivity than the parent strain under submerged culture at 30 degrees C for 24 h. About 70% of the total alpha-amylase activity in the M-33 culture filtrate was adsorbed onto starch granules. The electrophoretically homogeneous preparation of raw-starch-adsorbable alpha-amylase (molecular weight, 88,000), acid stable at pH 2, showed intensive raw-starch-digesting activity, dissolving corn starch granules completely. The preparation also exhibited a high synergistic effect with glucoamylase I. A mutant, M-72, with higher protease activity produced a raw cornstarch-unadsorbable alpha-amylase. The purified enzyme (molecular weight, 54,000), acid unstable, showed no digesting activity on raw corn starch and a lower synergistic effect with glucoamylase I in the hydrolysis of raw corn starch. The fungal alpha-amylase was therefore divided into two types, a novel type of raw-starch-digesting enzyme and a conventional type of raw-starch-nondigesting enzyme.
突变实验利用 N-甲基-N'-硝基-N-亚硝基胍降低了 Aspergillus ficum IFO 4320 的蛋白酶产量。在 30°C 下进行 24 小时的浸没培养时，蛋白酶阴性突变体 M-33 的α-淀粉酶活性比亲本菌株高。M-33 培养滤液中约 70%的总α-淀粉酶活性被吸附到淀粉颗粒上。未经处理的淀粉吸附性α-淀粉酶（分子量为 88000）的电泳均匀制剂在 pH 2 下稳定，具有强烈的原始淀粉消化活性，可完全溶解玉米淀粉颗粒。该制剂还与糖化酶 I 表现出很高的协同作用。具有更高蛋白酶活性的突变体 M-72 产生了未经处理的玉米淀粉吸附性α-淀粉酶。纯化后的酶（分子量为 54000），在酸性条件下不稳定，对未经处理的玉米淀粉没有消化活性，在水解未经处理的玉米淀粉时与糖化酶 I 的协同作用较低。因此，真菌α-淀粉酶分为两种类型，一种是新型的原始淀粉消化酶，另一种是传统的原始淀粉非消化酶。
