Gil G, Calvet V E, Asins G, Hegardt F G
Rev Esp Fisiol. 1983 Sep;39(3):259-66.
Incubation of four purified rat liver HMG-CoA reductase phosphatases, with ATP, ADP and AMP caused a concentration-dependent inactivation of enzyme activities. The nucleotides of guanine, cytosine and uracil produced similar effects to those by the nucleotides of adenine for the same number of phosphates present in the molecules. The greater the number of phosphate groups in nucleotides, the higher was the inhibition in reductase phosphatases observed. Preincubation of phosphatases with ATP and subsequent dilution did not diminish the inactivation effect, showing that nucleotides inhibit the enzyme prior to their binding to the substrate. A relationship was observed between those concentrations of nucleotides which produce 50% inactivation and the logarithm stability constant of Mg or Mn salts of nucleotides. ATP-inactivated enzymes were reactivated by Mn++ and to a lesser proportion by Mg++, the conclusion being that HMG-CoA reductase phosphatases have the characteristics of metalloenzymes.
四种纯化的大鼠肝脏HMG-CoA还原酶磷酸酶与ATP、ADP和AMP一起温育，会导致酶活性出现浓度依赖性失活。鸟嘌呤、胞嘧啶和尿嘧啶的核苷酸对于分子中存在相同数量磷酸基团的情况，产生了与腺嘌呤核苷酸类似的效应。核苷酸中磷酸基团的数量越多，观察到的还原酶磷酸酶抑制作用就越高。磷酸酶与ATP预温育并随后稀释，并不会减弱失活效应，这表明核苷酸在与底物结合之前就抑制了该酶。观察到产生50%失活的核苷酸浓度与核苷酸的镁盐或锰盐的对数稳定常数之间存在一种关系。ATP失活的酶可被Mn++重新激活，被Mg++重新激活的比例较小，结论是HMG-CoA还原酶磷酸酶具有金属酶的特性。
