Brockbank W J, Lynn K R
Biochim Biophys Acta. 1979 May 23;578(1):13-22. doi: 10.1016/0005-2795(79)90107-7.
Two groups of asclepains have been isolated from Asclepias syriaca L. (milk-weed) latex and a representative of each has been purified. Asclepains A3 and B5 are homogeneous proteins with molecular weights of 23 000 and 21 000, respectively. Both require a reducing and chelating agent for maximum activity and hydrolyze ester, amide and peptide bonds. The optimum pH for hydrolysis of casein is 7.5 to 8.5 for asclepain A3 and 7.0 to 7.5 for asclepain B5. Both enzymes are autolytic when active and are inhibited by p-chloromercuribenzoate, iodoacetic acid and sodium tetrathionate. Asclepains A3 and B5 each contain one titratable SH group per molecule and no bound carbohydrate. Each of the two enzymes has leucine as the N-terminal amino acid. There are notable differences in their amino acid compositions.
已从叙利亚马利筋（乳草）乳胶中分离出两组天冬蛋白酶，并对每组中的一种代表性酶进行了纯化。天冬蛋白酶A3和B5是均一的蛋白质，分子量分别为23000和21000。二者都需要还原剂和螯合剂才能达到最大活性，并且能水解酯键、酰胺键和肽键。天冬蛋白酶A3水解酪蛋白的最适pH为7.5至8.5，天冬蛋白酶B5为7.0至7.5。两种酶在有活性时都会发生自溶，并且会被对氯汞苯甲酸、碘乙酸和连四硫酸钠抑制。天冬蛋白酶A3和B5每分子均含有一个可滴定的巯基，且无结合碳水化合物。两种酶均以亮氨酸作为N端氨基酸。它们的氨基酸组成存在显著差异。
