Hammer Arne, Hodgson David R W, Cann Martin J
School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK.
Biochem J. 2006 Jun 1;396(2):215-8. doi: 10.1042/BJ20060372.
The Slr1991 adenylyl cyclase of the model prokaroyte Synechocystis PCC 6803 was stimulated 2-fold at 20 mM total C(i) (inorganic carbon) at pH 7.5 through an increase in k(cat). A dose response demonstrated an EC50 of 52.7 mM total C(i) at pH 6.5. Slr1991 adenylyl cyclase was activated by CO2, but not by HCO3-. CO2 regulation of adenylyl cyclase was conserved in the CyaB1 adenylyl cyclase of Anabaena PCC 7120. These adenylyl cyclases represent the only identified signalling enzymes directly activated by CO2. The findings prompt an urgent reassessment of the activating carbon species for proposed HCO3--activated adenylyl cyclases.
模式原核生物集胞藻PCC 6803的Slr1991腺苷酸环化酶在pH 7.5、总无机碳(C(i))浓度为20 mM时,通过催化常数(k(cat))的增加,活性提高了2倍。剂量反应表明,在pH 6.5时,总C(i)的半数有效浓度(EC50)为52.7 mM。Slr1991腺苷酸环化酶被CO2激活,但不被HCO3-激活。在鱼腥藻PCC 7120的CyaB1腺苷酸环化酶中,CO2对腺苷酸环化酶的调节作用得以保留。这些腺苷酸环化酶是唯一已确定的直接被CO2激活的信号酶。这些发现促使人们迫切重新评估对于所提出的HCO3-激活的腺苷酸环化酶而言的激活碳物种。