IDENTIFICATION OF ADENYLATE-CYCLASE ACTIVITY FROM ARTERIA CORONARIA OF CATTLE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 35  (12) , 1587-1594
Abstract
In 2 fractions obtained from bovine coronary arteries adenylate cyclase activity was identified and characterized. The adenylate cyclase activity of the 75,000 .times. g sediment showed a pH optimum at 7.4. The temperature dependence of this adenylate cyclase activity was linear when represented in the Arrhenius plot, and an Arrhenius activation energy of 13.2 kcal mol-1 was calculated for the enzyme reaction. The Km value of the enzyme to ATP was 6 .+-. 0.6 .cntdot. 10-4 M. The adenylate cyclase activity of the 75,000 .times. g sediment was stimulated by NaF. 5''AMP and adenosine inhibited the adenylate cyclase activity of the 75,000 .times. g sediment. With regard to the enzyme activity, Mn2+ and Co2+ replaced Mg2+, but not Ca2+. The monovalent cations Na+ and K+ did not influence the adenylate cyclase activity. In a particulate fraction containing plasma membranes, adenylate cyclase activity was also identified. This adenylate cyclase activity was stimulated by catecholamines, noradrenaline [norepinephrine] and isoproterenol. This stimulation can only be proved for the enzyme in the coronaries of 9 wk old and 2 yr old animals. The adenylate cyclase activity from the coronary arteries of adult animals was not affected by catecholamines. These findings are discussed with regard to hypertension frequently found in adult animals.