Hayano K, Fukui S
J Bacteriol. 1970 Mar;101(3):692-7. doi: 10.1128/jb.101.3.692-697.1970.
A 3-ketosucrose-degrading enzyme was purified 80-fold from the sonic extracts of Agrobacterium tumefaciens IAM 1525 grown on a sucrose-containing medium. The enzyme catalyzes hydrolysis of alpha-3-ketoglucosides such as 3-ketosucrose, 3-ketotrehalose, 3-ketomaltose, and 3-ketoglucose-1-phosphate but not of beta-3-ketoglucosides, beta-3-ketogalactosides, and other glycosides such as sucrose, trehalose, maltose, glucose-1-phosphate, cellobiose, lactose, or raffinose. From the strict substrate specificity of this enzyme, the name alpha-d-3-ketoglucoside 3-ketoglucohydrolase (trivial name, alpha-3-ketoglucosidase) was proposed. K(m) values for 3-ketosucrose and 3-ketotrehalose were 3.9 x 10(-3)m and 4.8 x 10(-3)m, respectively. Optimum pH was 8.0 to 8.3. 3-Ketoglucose, a reaction product from alpha-3-ketoglucosides by the enzyme, behaved as a strong inhibitor. Physiological significance of this enzyme in the disaccharide metabolism of this bacterium was discussed.
从在含蔗糖培养基上生长的根癌农杆菌IAM 1525的超声提取物中纯化出一种3-酮蔗糖降解酶，纯化倍数为80倍。该酶催化α-3-酮葡糖苷的水解，如3-酮蔗糖、3-酮海藻糖、3-酮麦芽糖和3-酮葡萄糖-1-磷酸，但不催化β-3-酮葡糖苷、β-3-酮半乳糖苷以及其他糖苷如蔗糖、海藻糖、麦芽糖、葡萄糖-1-磷酸、纤维二糖、乳糖或棉子糖的水解。根据该酶严格的底物特异性，提出了α-d-3-酮葡糖苷3-酮葡糖水解酶（俗名，α-3-酮葡糖苷酶）这一名称。3-酮蔗糖和3-酮海藻糖的米氏常数分别为3.9×10⁻³m和4.8×10⁻³m。最适pH为8.0至8.3。该酶作用于α-3-酮葡糖苷产生的反应产物3-酮葡萄糖表现为一种强效抑制剂。讨论了这种酶在该细菌二糖代谢中的生理意义。
