Kanemitsu F, Kawanishi I, Mizushima J, Okigaki T
Division of Clinical Laboratories, Kurashiki Central Hospital, Okayama, Japan.
Clin Biochem. 1990 Apr;23(2):121-5. doi: 10.1016/0009-9120(90)80022-b.
Three common variants of soluble cytoplasmic L-alanine:2-oxoglutarate aminotransferase (ALT, EC 2.6.1.2), sALT 1, 2-1 and 2, were isolated from normal human liver, and characterized by electrophoretic and kinetic analyses. The isoelectric point of sALT 1 was pH 6.45. sALT 2-1 was focused into three bands with pl 6.1, 6.2 and 6.45; sALT was focused into one band with pl 6.1. The electrophoretic mobilities of sALTs altered to the fast beta-globulin fraction after aging or papain treatment. Ammonia was produced during the latter, and the altered migration was considered to be caused by deamidation of sALT. The relative molecular mass of each of the enzymes was 110,000. Minor differences in the apparent Km values among the multiple forms for both L-alanine and 2-oxoglutarate were observed after incubation with 100 mumol/L of pyridoxal phosphate (PALP). PALP stimulation of the enzyme activities was also different. sALT 1 was more stable than sALT 2-1 and 2 after heat and urea treatments. In human sera from 1065 adult Japanese, sALT 2-1, a heterozygote form of sALT 1 and 2, was dominant.
从正常人肝脏中分离出可溶性细胞质L-丙氨酸：2-氧代戊二酸氨基转移酶（ALT，EC 2.6.1.2）的三种常见变体，即sALT 1、2-1和2，并通过电泳和动力学分析对其进行了表征。sALT 1的等电点为pH 6.45。sALT 2-1聚焦成三条带，其等电点分别为6.1、6.2和6.45；sALT聚焦成一条带，其等电点为6.1。老化或木瓜蛋白酶处理后，sALT的电泳迁移率改变为快速β球蛋白组分。在后者过程中产生了氨，迁移率的改变被认为是由sALT的脱酰胺作用引起的。每种酶的相对分子质量为110,000。用100μmol/L的磷酸吡哆醛（PALP）孵育后，观察到多种形式的酶对L-丙氨酸和2-氧代戊二酸的表观Km值存在微小差异。PALP对酶活性的刺激也不同。热和尿素处理后，sALT 1比sALT 2-1和2更稳定。在1065名日本成年人的血清中，sALT 2-1（sALT 1和2的杂合子形式）占主导地位。
