Botany Department, University of Reading, Whiteknights, RG6 2AS, Reading, U.K..
Planta. 1979 Oct;147(1):63-8. doi: 10.1007/BF00384592.
Rates of synthesis and turnover of nitrate reductase in Chlorella vulgaris have been estimated from density-labelling experiments. It is demonstrated that nitrate stimulates the rate of turnover of the enzyme. Upon transfer of Chlorella from ammonium to nitrate medium there is a rapid increase in nitrate reductase activity, only part of which is a consequence of increased de novo synthesis: there must also be considerable activation of existing enzyme. It is shown that, in the absence of nitrate, the enzyme is very stable in vivo. Upon transfer from nitrate to ammonium medium, synthesis of nitrate reductase is reduced below the limits of defection. These effects are separate from the reversible (ferricyanide-reactivatable) inactivation of the enzyme which is also observed.
已通过密度标记实验估算了小球藻中硝酸还原酶的合成和周转率。实验表明，硝酸能刺激酶的周转率。当小球藻从铵盐转移到硝酸盐培养基中时，硝酸还原酶的活性会迅速增加，而这部分增加并非仅仅是由于新合成的酶：一定有相当数量的现有酶被激活。实验表明，在没有硝酸盐的情况下，酶在体内非常稳定。当从硝酸盐转移到铵盐培养基中时，酶的合成会减少到检测不到的水平。这些影响与酶的可逆（铁氰化物可恢复失活）失活分开。
