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Biomedical subjects

S S Pan

Publications and source records attributed to S S Pan.

41 records · Page 3Linked to original sources
PubMed1971

Invitro formation of assimilatory reduced nicotinamide adenine dinucleotide phosphate: nitrate reductase from a Neurospora mutant and a component of molybdenum-enzymes.

An active Neurospora-like assimilatory NADPH-nitrate reductase (EC 1.6.6.2), which can be formed in vitro by incubation of extracts of nitrate-induced Neurospora crassa mutant nit-1 with extracts of (a) certain other nonallelic nitrate reductase mutants, (b) uninduced wild type, or (c) xanthine oxidizing and liver aldehyde-oxidase systems was also formed by combination of the nit-1 extract with other acid-treated enzymes known to contain molybdenum. These molybdenum enzymes included (a) nitrogenase, or its molybdenum-iron protein, from Clostridium, Azotobacter, and soybeannodule bacteroids, (b) bovine liver sulfite oxidase, (c) respiratory formate-nitrate reductase from Escherichia coli, (d) NADH-nitrate reductase from foxtail grass (Setaria faberii), and (e) FADH(2)- and reduced methyl viologennitrate reductase preparations from certain Neurospora mutants. Several molybdenum-amino-acid complexes, as possible catalytic models of nitrogenase, were inactive (as were some previously tested 20 nonmolybdenum enzymes) in place of the acid-treated molybdenum-containing enzymes. The results imply the existence of a molybdenum-containing component shared by the known molybdenum-enzymes.

Animals↗
PubMedDate not supplied

Alkylation of DNA with aziridine produced during the hydrolysis of N,N',N''-triethylenethiophosphoramide.

A reaction pathway by which thiotepa (N,N',N''-triethylenethiophosphoramide) and tepa (N,N',N''-triethylenethiophosphoramide), its major metabolite in humans, alkylate and depurinate DNA involves hydrolysis to aziridine (ethylene imine), a highly reactive monofunctional alkylating agent. Hydrolytic cleavage of an N-P bond of thiotepa releases aziridine which reacts with DNA, resulting in depurination and formation of the stable N-7 adduct 7-(2-aminoethyl)guanine and an aminoethyl adduct of adenine. Chromatographically identical alkylated products were observed in the reaction of thiotepa and tepa with individual nucleosides. Adducts with deoxycytidine or thymidine were not detected. Aziridine was measured by HPLC after derivatization with 1,2-naphthoquinone 4-sulfate. On the basis of the identity of the DNA adducts and the rate of formation of aziridine by hydrolysis in vitro, thiotepa is concluded to be a lipophilic, stabilized form of aziridine which serves as a cell-penetrating carrier of aziridine.

Alkylating Agents↗