摘要
大豆叶片的α—淀粉酶对SH—反应剂不敏感,在pH3.6时失活Ca^(2+)使它的耐热性提高至70℃.β—淀粉酶对SH—反应剂敏感,耐酸至pH 2.3,耐热至60℃. 随着叶龄的增长α—淀粉酶的同工酶数目增加,此酶在一般情况下不需要添加Ca^(2+),EDTA对它起不可逆的失活作用,β—极限糊精及Ca^(2+)可排除EDTA对酶的影响。此酶可能是Ca—金属酶,Ca^(2+)与酶结合紧密,它位于酶的活性中心或附近。 在体外,大豆叶片α—淀粉酶可被自身的淀粉粒吸附,但容易被 pH5的醋酸缓冲液洗脱。
Soybean leaf α-amylase was insensitive
to sulfhydryl reagents (Table 1) and inactive
at pH 3.6. In the presence of CaC1_2 its resis-
tance to heat increased from 60℃ to 70℃(Fig.
).β-amylase was sensitive to sulfhydryl
reagents but stable at 60℃ and pH 2.3 (Fig. 2).
Disc gel electrophoresis showed that soy-
bean leaf α-amylase had consists of several
isozymes (Fig. 1). This enzyme did not
require Ca^(2+) for its activity usually and the
enzyme activity was not changed by dialysis.
It was inactivated by EDTA and further dialy-
sis could not restore the enzyme activity (Tabler
2).β-limit dextrin could protect this enzyme
from the inactivation caused by EDTA.α-amy-
lase was considered to be a Ca-metallo-enzyme,
Ca^(2+) was firmly bound to the enzyme and located
at or near the substrate binding site. In vitro
soybean leaf α-amylase could be adsorbed on
its starch granule and eluted easily by acetate
buffer at pH 5.
关键词
大豆
叶片
淀粉酶
soybean leaves
αamylase
β-amylase
