Enzyme

About: Enzyme is a research topic. Over the lifetime, 32846 publications have been published within this topic receiving 1180957 citations. The topic is also known as: Enzyme.

Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme.

Abstract: Nitric oxide mediates vascular relaxing effects of endothelial cells, cytotoxic actions of macrophages and neutrophils, and influences of excitatory amino acids on cerebellar cyclic GMP. Its enzymatic formation from arginine by a soluble enzyme associated with stoichiometric production of citrulline requires NADPH and Ca2+. We show that nitric oxide synthetase activity requires calmodulin. Utilizing a 2',5'-ADP affinity column eluted with NADPH, we have purified nitric oxide synthetase 6000-fold to homogeneity from rat cerebellum. The purified enzyme migrates as a single 150-kDa band on SDS/PAGE, and the native enzyme appears to be a monomer.

Angiotensin II stimulates NADH and NADPH oxidase activity in cultured vascular smooth muscle cells.

Abstract: The signaling pathways involved in the long-term metabolic effects of angiotensin II (Ang II) in vascular smooth muscle cells are incompletely understood but include the generation of molecules likely to affect oxidase activity. We examined the ability of Ang II to stimulate superoxide anion formation and investigated the identity of the oxidases responsible for its production. Treatment of vascular smooth muscle cells with Ang II for 4 to 6 hours caused a 2.7 +/- 0.4-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. This superoxide appeared to result from activation of both the NADPH and NADH oxidases. NADPH oxidase activity increased from 3.23 +/- 0.61 to 11.80 +/- 1.72 nmol O2-/min per milligram protein after 4 hours of Ang II, whereas NADH oxidase activity increased from 16.76 +/- 2.13 to 45.00 +/- 4.57 nmol O2-/min per milligram protein. The NADPH oxidase activity was stimulated by exogenous phosphatidic and arachidonic acids and was partially inhibited by the specific inhibitor diphenylene iodinium. NADH oxidase activity was increased by arachidonic and linoleic acids, was insensitive to exogenous phosphatidic acid, and was inhibited by high concentrations of quinacrine. Both of these oxidases appear to reside in the plasma membrane, on the basis of migration of the activity after cellular fractionation and their apparent insensitivity to the mitochondrial poison KCN. These observations suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.

A novel heterodimeric cysteine protease is required for interleukin-1 beta processing in monocytes.

Abstract: Interleukin-1 beta (IL-1 beta)-converting enzyme cleaves the IL-1 beta precursor to mature IL-1 beta, an important mediator of inflammation. The identification of the enzyme as a unique cysteine protease and the design of potent peptide aldehyde inhibitors are described. Purification and cloning of the complementary DNA indicates that IL-1 beta-converting enzyme is composed of two nonidentical subunits that are derived from a single proenzyme, possibly by autoproteolysis. Selective inhibition of the enzyme in human blood monocytes blocks production of mature IL-1 beta, indicating that it is a potential therapeutic target.

Adenosine 3',5'-phosphate in biological materials. I. Purification and properties of cyclic 3',5'-nucleotide phosphodiesterase and use of this enzyme to characterize adenosine 3',5'-phosphate in human urine.

Abstract: The detection and measurement of adenosine 3’) 5’-phosphate are complicated by the extremely low levels present in most biological materials and by the sensitivity of the standard assay to activation or inhibition by substances native to the tissue or fluid under study (l-3). These problems made the availability of a specific means of destroying adenosine 3’,5’-phosphate very desirable. An enzymatic activity capable of destroying adenosine 3’,5’phosphate was detected in various mammalian tissues several years ago (4). Investigation showed that this activity was due to a magnesium-dependent phosphodiesterase that catalyzed the hydrolysis of the cyclic nucleotide at the 3’-position, yielding adenosine 5’-phosphate. It was found to be inhibited by the methyl xanthines (4, 5) and stimulated by imidazole (5). No other physiological mechanism has been found by which the action of adenosine 3’) 5’-phosphate could be terminated. Hence, these data indicated a significant role for the enzyme in the control of the levels of adenosine 3’,5’-phosphate present in biological systems. This report deals with the purification, properties, and distribution of the cyclic 3’, 5’-nucleotide phosphodiesterase, the occurrence of adenosine 3’,5’-phosphate in human urine, and the use of purified samples of the enzyme to aid in the identification and measurement of this adenosine 3’) 5’-phosphate.