RESUMO
Zhang et al. (Research Articles, 11 November 2005, p. 996) reported that obestatin, a peptide derived from the ghrelin precursor, activated the orphan G protein-coupled receptor GPR39. However, we found that I125-obestatin does not bind GPR39 and observed no effects of obestatin on GPR39-transfected cells in various functional assays (cyclic adenosine monophosphate production, calcium mobilization, and GPR39 internalization). Our results indicate that obestatin is not the cognate ligand for GPR39.
Assuntos
Hormônios Peptídicos/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Células CHO , Cálcio/metabolismo , Membrana Celular/metabolismo , Colforsina/farmacologia , Cricetinae , Cricetulus , AMP Cíclico/metabolismo , Grelina , Humanos , Ligantes , Dados de Sequência Molecular , Hormônios Peptídicos/genética , Hormônios Peptídicos/farmacologia , Hipófise/citologia , Hipófise/metabolismo , Ligação Proteica , Receptores Acoplados a Proteínas G/genética , TransfecçãoRESUMO
A variant alkaline phosphatase (ALP), with heat-sensitivity characteristics similar to that of the bone type, was found in the serum of a patient suffering from lung cancer. In disc polyacrylamide gel electrophoretic studies most of this enzyme had migrated to the region corresponding to liver ALP, with the remainder affecting bone ALP. Like kidney ALP, this ALP was markedly inhibited by 0.5 mmol/l L-cysteine. The K(m) of this ALP for p-nitrophenylphosphate was 0.39 mmol/l, similar to that of kidney ALP. The sugar moiety of this enzyme bore greater resemblance to that of kidney ALP than liver or bone ALP. However, immunoprecipitation of this particular ALP was strong with a monoclonal antibody against liver ALP and moderate with an antibody against bone ALP.