Kim C H, Kwon S T, Taniguchi H, Lee D S
Genetic Engineering Research Institute, K.I.S.T., Yusung-ku, Taejon, South Korea.
Biochim Biophys Acta. 1992 Aug 21;1122(3):243-50. doi: 10.1016/0167-4838(92)90399-x.
Raw starch-digesting amylase (BF-2A, 93,000 Da) from Bacillus circulans F-2 was converted into two components during digestion with subtilisin. The two components were separated and designated BF-2A' (63 kDa) and BF-2B (30 kDa), respectively. BF-2A' exhibited the same hydrolysis curve for soluble starch as the original amylase (BF-2A). Moreover, the catalytic activities of original and modified enzymes were indistinguishable in Km, Vmax and in their specific activity for soluble starch hydrolysis. However, its absorbability and digestibility on raw starch was greatly decreased. Furthermore, the enzymatic action pattern on soluble starch was differed greatly from that of BF-2A. The stability of the enzymes decreased below pH 5.5 and at 50 degrees C, while it was quite stable even at pH 12. On the other hand, the smaller peptide (BF-2B) could be adsorbed onto raw starch. From these results, it is suggested that the larger peptide (BF-2A') has a region responsible for the expression of the enzyme activity to hydrolyze soluble substrate, and the smaller peptide (BF-2B) plays a role on raw starch adsorption and also contributes to the original enzyme-to-enzyme stabilization. A proposed model of the raw-starch-digesting enzyme from this strain is extensively discussed.
来自环状芽孢杆菌F-2的生淀粉消化淀粉酶（BF-2A，93,000 Da）在用枯草杆菌蛋白酶消化过程中被转化为两个组分。这两个组分被分离出来，分别命名为BF-2A'（63 kDa）和BF-2B（30 kDa）。BF-2A'对可溶性淀粉的水解曲线与原始淀粉酶（BF-2A）相同。此外，原始酶和修饰酶在Km、Vmax以及对可溶性淀粉水解的比活性方面的催化活性没有区别。然而，它对生淀粉的吸附性和消化性大大降低。此外，其对可溶性淀粉的酶作用模式与BF-2A有很大不同。这些酶在pH 5.5以下和50℃时稳定性降低，而即使在pH 12时也相当稳定。另一方面，较小的肽（BF-2B）可以吸附到生淀粉上。从这些结果表明，较大的肽（BF-2A'）有一个负责水解可溶性底物的酶活性表达的区域，而较小的肽（BF-2B）在生淀粉吸附中起作用，并且也有助于原始酶的稳定性。本文广泛讨论了该菌株生淀粉消化酶的一个 proposed model。 （注：这里“proposed model”不太明确准确含义，可能是“提出的模型”之类的，按原文保留）
