赤霉酸对枯草杆菌α—淀粉酶形成的作用

在枯草杆菌细胞的培养基中加入赤霉酸,可以显著地促进α-淀粉酶的形成。环式磷酸腺苷和三磷酸腺苷能够模拟赤霉酸促进α-淀粉酶合成的作用。我们还观察了葡萄糖对α-淀粉酶产生的影响。当细菌在含有谷氨酸的培养基中生长时,加入葡萄糖能使α-淀粉酶的合成受到抑制。葡萄糖对α-淀粉酶形成的抑制作用可以被赤霉酸所消除。此外,在有赤霉酸存在时,枯草杆菌α-淀粉酶的合成受到放线菌素D的抑制。赤霉酸对α-淀粉酶合成的作用可能是在转录水平上受到环式磷酸腺苷的调节。     

REGULATION OF NITRATE REDUCTASE ACTIVITY IN RICE

The properties of NR from rice varieties Yuanfengzao and Jingyin 127 are the same in molecular weight of native enzyme and subunit, optimum pH, K_m value for substrates NO_3~- and NADH, stability in vitro and immunological characteristics. The decay rate in vitro of the activity of the partially purified NR from Yuanfengzao is 20％ lower than that from Jingyin 127. The results from antiserum titration and rocket immunoelectrophoresis indicated that the amount of NR in Yuanfengzao is about 1.5 times more than that in Jingyin 127. Further study on in vivo incorporation of ~3H-labeled amino acids into NR revealed that the rate of NR synthesis in Yuanfengzao is obviously higher than that in Jingyin 127. In vitro translation of mRNA showed that the products of NR-mRNA per unit of total mRNA of Yuanfengzao is much more than that of Jingyin 127. It is concluded that, therefore, NR activity in rice is regulated through NR synthesis and NR-inhibitory protein(s) system, the former is further controlled at the lev     

水稻硝酸还原酶活力的调节

水稻品种原丰早(籼稻)和京引127(粳稻)的NR在分子量、亚基组成、体外稳定性、免疫学特性、最适pH以及对底物的K_m值等是相同的。在部分纯化的酶液中,原丰早的酶活力衰减速率比京引127慢20％左右。火箭免疫电泳和抗血清滴定结果指出原丰早NR的量比京引127多1.5倍。~3H-氨基酸体内参入NR的试验表明在诱导条件下原丰早NR的从头合成量明显高于京引127。原丰早中NR-mRNA的体外翻译产物也大大高于京引127。可见水稻体内NR活力受酶的合成和酶的钝化系统的调节,酶的合成又受NR-mRNA转录的控制。