Human fat cell adenylate cyclase

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Abstract
Summary The effects of guanine nucleotides on basal and parathyroid hormone-stimulated adenylate cyclase of human fat cell ghosts were studied. GTP (10−7–10−3 M) caused a dose-dependent inhibition of basal enzyme activity, but it had no significant effect on PTH-stimulated rates of cAMP-formation. The guanine nucleotide analogue 5′-guanylyl-imidodiphosphate GMP (PNP) when applied in the same concentration range, stimulated basal as well as PTH-activated adenylate cyclase activity up to 300%. GMP (PNP) activation was non-linear with time. PTH-activated the human fat cell adenylate cyclase via an individual receptor distinct from beta-adrenergic receptor sites.