RESUMO
Cyclic GMP is a key messenger molecule in several cellular processes. It is also an important modulator of immune response. In this paper we summarize current data concerning regulatory and modulatory function of cGMP in the cells of immune system. Metabolism of the nucleotide as well as its role in processes such as cell proliferation, differentiation, chemotaxis and release of mediators are described. The fields of future research are indicated as well.
Assuntos
GMP Cíclico/metabolismo , Imunidade Celular/fisiologia , Animais , Adesão Celular/fisiologia , Diferenciação Celular/fisiologia , Divisão Celular/fisiologia , Quimiotaxia/fisiologia , Humanos , Fagocitose/imunologiaRESUMO
A phosphatase cleaving the pyrophosphate bond in diphosphonucleotides and phosphodiester bond in various phosphodiesters (pH optimum at 6.25) was purified from yellow lupin (Lupinus luteus L.) seeds. The enzyme is 75 kDa monomeric glycoprotein (pI=6.4) with 4.4% of carbohydrate (mannose, N-acetylglucosamine, fucose and xylose). Analysis of its partial amino acid sequence (8 peptides, 101 amino acid residues) together with no divalent cation requirements for catalysis points out that the purified enzyme is different from known plant pyrophosphate cleaving enzymes (apyrases and inorganic pyrophosphatases). Its physiological role could be related to a regulation of diphosphonucleotides level in plant metabolism.
Assuntos
Monoéster Fosfórico Hidrolases/química , Plantas/enzimologia , Sequência de Aminoácidos , Cromatografia de Afinidade , Cromatografia Líquida de Alta Pressão , Cromatografia por Troca Iônica , Ácido Edético , Eletroforese em Gel de Poliacrilamida , Metais , Dados de Sequência Molecular , Nucleotidases/química , Fragmentos de Peptídeos , Monoéster Fosfórico Hidrolases/isolamento & purificação , Monoéster Fosfórico Hidrolases/metabolismo , Sementes/enzimologia , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
Cyclic GMP (cGMP), a key messenger in several signal transduction pathways, is synthesized from GTP by a family of enzymes termed guanylyl cyclases, which are found in two forms: cytosolic (soluble) and membrane-bound (particulate). The past decade has brought significant progress in understanding the molecular mechanisms that underlie the regulation of particulate guanylyl cyclases and new members of their family have been identified. It has become more evident that the basic mechanism of catalysis of guanylyl cyclases is analogous to that recognized in adenylyl cyclases. Here we review the known basic mechanisms that contribute to the regulation of particulate guanylyl cyclases.
