Biomedical subjects
P Greenbaum
Publications and source records attributed to P Greenbaum.
Fear-based advertising and the increase in psychiatric hospitalization of adolescents.
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Preparation and some properties of homogeneous Neurospora crassa assimilatory NADPH-nitrite reductase.
The Neurospora crassa assimilatory NADPH-nitrite reductase (NAD(P)H: nitrite oxidoreductase, EC 1.6.6.4), which catalyzes the NADPH-dependent formation of ammonia from nitrite, has been purified to homogeneity as judged by polyacrylamide gel electrophoresis. The specific activity of the purified enzyme is 26.9 mumol nitrite reduced/min per mg protein, which corresponds to a turnover number of 7800 min(-1). The enzyme also has associated NADH-nitrite reductase, NADPH-hydroxylamine reductase and NADH-hydroxylamine reductase activities. The stoichiometry of 3 mol NADPH oxidized per mol nitrite reduced and ammonia formed has been confirmed. The visible absorption spectrum of the nitrite reductase reveals maxima at 280,390 (Soret) and 580 (alpha) nm. The latter bands are indicative of the occurrence of siroheme as a prosthetic group. The A280nm/A390nm ratio of 7.0 and the Soret/alpha ratio of 3.8 are compatible with values reported for other purified siroheme-containing enzymes. These results are discussed in terms of the comparative biochemistry of various enzymes involved in nitrite, hydroxylamine and sulfite metabolism in Neurospora crassa and other organisms.
Postemergence growth of the ovarian follicles of Aedes aegypti.
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Studies on the in vitro inactivation of the Neurospora crassa assimilatory nitrite reductase in the presence of reduced pyridine nucleotides plus flavin.
In vitro inactivation of Neurospora crassa nitrite reductase (NAD(P)H: nitrite oxidoreductase, EC 1.6.6.4) can be obtained by preincubation of the enzyme with reduced pyridine nucleotide plus FAD. The presence of nitrite or hydroxylamine, electron acceptors for the N. crassa nitrite reductase, or cyanide, sulfite or arsenite, competitive inhibitors with respect to nitrite of this enzyme, protects the enzyme against this inactivation. Anaerobic experiments reveal that oxygen is required in order to obtain complete inactivation of nitrite reductase by preincubation with reduced pyridine nucleotide plus FAD. Also, inactivation is prevented if catalase is included in the preincubation mixture. The presence of hydrogen peroxide in the preincubation mixture increases the sensitivity of nitrite reductase to the in vitro FAD-dependent NAD(P)H inactivation. Neither electron acceptors, competitive inhibitors nor catalase, agents which protect the enzyme against the FAD-dependent NAD(P)H inactivation, can reverse this process once it has occurred.
The inhibition of the Neurospora crassa nitrate reductase complex by metal-binding agents.
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