Kearse F J, Dixon E
Am J Physiol. 1985 Dec;249(6 Pt 2):R740-6. doi: 10.1152/ajpregu.1985.249.6.R740.
Previous studies have demonstrated the presence of two type III hexokinase isozymes in pig mature erythrocytes. The prevalence of a specific isozyme species is an age-dependent phenomenon. The mature erythrocyte of young adult pigs (less than 6 mo old) possess an isozyme that has an apparent Km for glucose that is lower than in adult pigs. The data in this report suggest several basic differences between the two isozymes. D-Mannoheptulose, a structural analogue of glucose, was observed to differentially inhibit the isozymes. The young adult isozyme tended to be heat sensitive when compared with adult isozymes. Carboxypeptidase B and trypsin inhibited the activity of both isozymes, but the young adult isozyme was most dramatically affected by carboxypeptidase B. When the two isozymes were incubated in the presence of two sulfhydryl group inhibitors, HgCl2 and 5,5'-dithiobis [2-nitrobenzoic acid] (DTNB), the young adult isozyme exhibited the greater inhibition in the presence of DTNB. The data suggest that the young adult isozyme exhibited pronounced differences in activity when incubated in the presence of DTNB and carboxypeptidase B. These two agents may be used as probes to further characterize the properties of the two isozymes.
先前的研究已证实在猪的成熟红细胞中存在两种III型己糖激酶同工酶。特定同工酶种类的流行是一种年龄依赖性现象。年轻成年猪（小于6月龄）的成熟红细胞拥有一种同工酶，其对葡萄糖的表观Km低于成年猪。本报告中的数据表明这两种同工酶之间存在一些基本差异。观察到葡萄糖的结构类似物D-甘露庚酮糖对同工酶有不同的抑制作用。与成年同工酶相比，年轻成年同工酶往往对热敏感。羧肽酶B和胰蛋白酶抑制两种同工酶的活性，但年轻成年同工酶受羧肽酶B的影响最为显著。当两种同工酶在两种巯基抑制剂HgCl2和5,5'-二硫代双[2-硝基苯甲酸]（DTNB）存在下孵育时，年轻成年同工酶在DTNB存在下表现出更大的抑制作用。数据表明，当在DTNB和羧肽酶B存在下孵育时，年轻成年同工酶在活性上表现出明显差异。这两种试剂可用作进一步表征两种同工酶特性的探针。
