Thimann Laboratories, University of California, Santa Cruz, California 95064.
Plant Physiol. 1978 Apr;61(4):501-5. doi: 10.1104/pp.61.4.501.
Two proteases isolated from senescent oat (Avena sativa) leaves have been subjected to further study. One of these, an acid protease active at pH 4.2, is inhibited by phenylmethylsulfonyl fluoride (PMSF) but not by iodoacetamide (IAc). The other, active at pH 6.6, is inhibited by both PMSF and IAc. These results, together with previously reported evidence that mercaptoethanol stimulates the activity of only the neutral protease, are taken to indicate that the acid protease is probably of the serine type, whereas the neutral enzyme is of the sulfhydryl type. Both enzymes are inhibited by irradiation in the presence of rose bengal, a selective histidine modification reagent. The acid protease was completely unaffected by chelators, but data on the neutral protease were equivocal.All protein substrates tested were attacked by both enzymes, though at strikingly different rates. Characterization of the digestion products, with denatured hemoglobin as substrate, indicated that the acidic enzyme is an endoprotease, while the neutral one is an exoprotease. Evidence is presented that these proteases undergo autolysis in vitro.
已对从衰老的燕麦（Avena sativa）叶片中分离出的两种蛋白酶进行了进一步研究。其中一种是在 pH 值为 4.2 时具有活性的酸性蛋白酶，被苯甲基磺酰氟（PMSF）抑制，但不受碘乙酰胺（IAc）抑制。另一种在 pH 值为 6.6 时具有活性，同时被 PMSF 和 IAc 抑制。这些结果，以及先前报道的表明只有巯基乙醇能刺激中性蛋白酶活性的证据，表明酸性蛋白酶可能是丝氨酸类型的，而中性酶是巯基类型的。两种酶在玫瑰红孟加拉存在下被辐照抑制，这是一种选择性的组氨酸修饰试剂。酸性蛋白酶完全不受螯合剂的影响，但中性蛋白酶的数据则存在争议。所有测试的蛋白质底物都被两种酶攻击，尽管速率明显不同。以变性血红蛋白为底物的消化产物的特征表明，酸性酶是内肽酶，而中性酶是外肽酶。有证据表明这些蛋白酶在体外发生自溶。
