Multiphasic activation of smooth muscle adenylate cyclase by pretreatment with guanyl-5′-yl imidodiphosphate (Gpp(NH)p) suggests multiple enzyme populations
| Autor: | Stanley G. Korenman, J.Frederick Krall, Rochelle E. Stahl, Marianne Frolich |
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| Rok vydání: | 1982 |
| Předmět: |
GTP'
Kinetics Biophysics Adenylate kinase Biochemistry Cyclase Catalysis Smooth muscle Animals Nucleotide Molecular Biology chemistry.chemical_classification Guanylyl Imidodiphosphate Chemistry Uterus Muscle Smooth Rats Inbred Strains Rats Enzyme Activation Isoenzymes Enzyme Female Guanosine Triphosphate Adenylyl Cyclases |
| Zdroj: | Archives of Biochemistry and Biophysics. 217:473-478 |
| ISSN: | 0003-9861 |
| DOI: | 10.1016/0003-9861(82)90526-4 |
| Popis: | The activation of uterine smooth muscle adenylate cyclase was studied by pretreating the particulate form of the enzyme with the GTP analog guanyl-5′-yl imidodiphosphate (Gpp(NH)p). Pretreatment with Gpp(NH)p left the enzyme in an irreversibly activated state which survived subsequent washing in guanyl nucleotide-free buffer. Activation under these conditions was multiphasic with rapid and slow components. At 23 °C slow activation proceeded at about 1 10 th the rate of rapid activation. The onset of the slow phase took longer at lower temperatures. Routine adenylate cyclase assay conditions (conversion of [ 32 P]ATP to cyclic [ 32 P]AMP) carried out without pretreatment probably characterized the rapidly activated component. The simplest kinetic model suggests not only the generally accepted two-step association reaction, but also implies the existence of more than one enzyme form, each of which is characterized by a separate activation rate. The complex kinetics of activation might be explained by a heterogeneous mixture of unassociated and preassociated nucleotide binding and catalytic subunits. |
| Databáze: | OpenAIRE |
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