Hamet P, Baird C E, Hardman J G
J Cyclic Nucleotide Res. 1978 Jun;4(3):183-99.
Characteristics of adenylate cyclase activity of the intima plus media layer of pig coronary arteries have been studied. Enzyme activity in the 10,000 xg particulate fraction was linear with respect to time and protein during short incubations. Linear kinetics were observed for MgATP as a substrate and free Mg2+ as an activator. Mn2+ added in excess of ATP concentrations was only slightly stimulatory or inhibitory. Adenosine, GTP and GPP(N)P inhibited enzyme activity. Adenosine decreased the Vmax and the Ka for Mg2+ but had no effect on the Km for MgATP. The inhibition by adenosine was reversible, while that by GPP(N)P appeared to be irreversible. Although preincubation of the enzyme with GPP(N)P for short times caused irreversible inhibition, preincubation for more than 15 min caused up to 3-fold activation. Isoproterenol added to the incubation produced no or very slight stimulation with or without GPP(N)P or GTP, and preincubation with isoproterenol alone caused irreversible inhibition. However, preincubation with isoproterenol plus GPP(N)P for 30 min caused irreversible activation exceeding that observed with GPP(N)P alone. These observations suggest that vascular adenylate cyclase, like the enzyme from the other tissues, can exist in multiple states of activity and responsiveness.
对猪冠状动脉内膜加中膜层的腺苷酸环化酶活性特征进行了研究。在短时间孵育过程中，10,000 xg微粒部分中的酶活性与时间和蛋白质呈线性关系。观察到以MgATP为底物和游离Mg2+为激活剂时呈线性动力学。当Mn2+的添加量超过ATP浓度时，其刺激或抑制作用较弱。腺苷、GTP和GPP(N)P抑制酶活性。腺苷降低了Mg2+的Vmax和Ka，但对MgATP的Km没有影响。腺苷的抑制作用是可逆的，而GPP(N)P的抑制作用似乎是不可逆的。尽管酶与GPP(N)P短时间预孵育会导致不可逆抑制，但预孵育超过15分钟会导致高达3倍的激活。在有或没有GPP(N)P或GTP的情况下，孵育时加入异丙肾上腺素不会产生刺激或刺激作用非常轻微，单独用异丙肾上腺素预孵育会导致不可逆抑制。然而，异丙肾上腺素加GPP(N)P预孵育30分钟会导致不可逆激活，超过单独用GPP(N)P观察到的激活程度。这些观察结果表明，血管腺苷酸环化酶与其他组织中的酶一样，可以存在多种活性和反应状态。
