大豆叶片尿囊素酶的纯化和性质

被纯化的 L—ALNase比活是 819 nkat/mg,酶的纯度提高了738倍,得率为27％。最适pH 7.4,K_m为13.7 mmol/L ALN,对还原剂和巯基试剂敏感,但5 mmol/L的抗坏血酸可提高酶活26％。磷酸盐和KCN有些抑制作用,但Mn~(2+)无活化作用。7.5％ PAGE,ANP定位测定,是 R_f 0.62、0.64、0.68、0.70和 0.725个同功酶的混合物。

Purification and Properties of Allantoinase from Soybean Leaves

Allantoinase is a key enzyme inthe metabolism of ureides in soybean.A 738--fold purification of allantoinasewith a yield of 27% from soybeanleaves by pertial denaturation, solubi-lization, ammonium sulfate fractiona-tion, gel filtration and ion exchangechromatography is described. The spe-cific activity of the purified enzymewas 819 nkat/mg, the pH optimumwas 7. 4 and the K_m values for allantoinwas 13. 7 mmol/L. This enzyme wasparticularly sensitive to reducing agentsand inhibitors of sulfhydryl group-de-pendent enzymes, but the activity couldbe enhanced by 5 mmol/L ascorbate to26%. Phosphate and KCN had someinhibitory effect, but Mn~(2+) no activit-ing effect. 7. 5% PAGE combinedwith localizing assay with ANP for theactivity showed that the allantoinasepurified from soybean leaves had fiveisoenzymes.