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Biomedical subjects

D Hendlin

Publications and source records attributed to D Hendlin.

30 records · Page 2Linked to original sources
PubMed1967

Phosphohydrolases of a Bacillus subtilis mutant accumulating inosine and hypoxanthine.

Although adenine-requiring auxotrophs of Bacillus subtilis accumulate large quantities of inosine or hypoxanthine, or of both, they do not accumulate inosine-5'-monophosphate (IMP). Experiments directed at understanding this phenomenon were conducted with an adenineless auxotroph and with a mutant derived from it which lacked alkaline phosphohydrolase. It was found that B. subtilis contains four different phosphohydrolases. Only one is an extracellular enzyme; it is a 5'-nucleotide phosphohydrolase which can be inhibited by addition of CuSO(4) to the medium. Of the three cellular enzymes, only one, an acid phosphohydrolase, cannot attack 5'-nucleotides; this enzyme is not repressed by inorganic phosphate. One of the two remaining surface-bound enzymes is a nonspecific alkaline phosphohydrolase which attacks both 5'-nucleotides and p-nitrophenyl phosphate; this is the only phosphohydrolase that is markedly repressed by inorganic phosphate. The other surface-bound enzyme is a nonrepressible 5'-nucleotide phosphohydrolase with double pH optima: one at neutrality and the other near pH 9.0. The experiments indicate that the absence of IMP in the extracellular broth is due to degradation of internally accumulated IMP to inosine by the cellular 5'-nucleotide phosphohydrolase.

Bacillus subtilis↗
PubMed1966

Production of guanosine-5'-monophosphate and inosine-5'-monophosphate by fermentation.

A biotin-requiring coryneform bacterium which produces glutamic acid was mutated to adenine dependency. The adenine-requiring strain, which excreted insoine-5'-monophosphate (IMP), was further mutated to xanthine dependency. As expected, IMP was also excreted by this mutant. The mutant strain was reverted to xanthine independence in an attempt to obtain a culture with an altered IMP dehydrogenase which would be less sensitive to feedback inhibition by guanosine-5'-monophosphate (GMP). A revertant was obtained which produced GMP and IMP, each at 0.5 g per liter. The reversion to xanthine independence had resulted in a concomitant requirement for isoleucine, leucine, and valine. Further mutation to increased nutritional requirements led to culture MB-1802, which accumulated 1 g per liter each of GMP and IMP. Both nucleotides were isolated in pure form. The concentrations of GMP and IMP produced by MB-1802 were four times that of cytidylate, uridylate, or adenylate, indicating that the mechanism of GMP and IMP production was direct and not via ribonucleic acid breakdown.

Journal Article↗
PubMed1965

Production of xanthosine-5'-monophosphate and inosine-5'-monophosphate by auxotrophic mutants of a coryneform bacterium.

Although most microorganisms with genetic blocks in the purine nucleotide sequence excrete breakdown products, a coryneform bacterium was found to accumulate intact 5'-nucleotides in the extracellular medium. Adenineless mutants accumulated 0.4 to 0.6 g of inosine-5'-monophosphate per liter of broth. The yield of this nucleotide was increased to 0.8 to 0.9 g per liter when such mutants were mutated to xanthine dependence. Induction of a specific guanine requirement in adenineless auxotrophs resulted in cultures capable of producing high yields of xanthosine-5'-monophosphate (3 to 4 g per liter). Pure xanthosine-5'-monophosphate was isolated from broth by a procedure involving ion-exchange chromatography, charcoal adsorption, and barium precipitation.

Corynebacterium↗
PubMedDate not supplied

Cefoxitin and cephamycins: microbiological studies.

The cephamycins are a family of beta-lactam antibiotics that are produced by actinomycetes and are structurally similar to the cephalosporins. They are characterized by the presence of a 7-alpha-methoxyl group, which confers unusually high resistance to beta-lactamases. Cefoxitin, the first semisynthetic cephamycin, is resistant to almost all beta-lactamases. Cefoxitin retains the 3-carbamoyl group of cephamycin C and thus has excellent metabolic stability. Cefoxitin is bactericidal and almost devoid of any inoculum effect. Active against many cephalothin-resistant gram-negative bacteria, cefoxitin demonstrates a very broad spectrum that includes indole-positive Proteus and many strains of Serratia. In contrast to that of the cephalosporins, cefoxitin's spectrum of activity against anaerobic pathogens includes Bacteroides fragilis. The therapeutic effectiveness of cefoxitin in experimental infections in mice confirms the excellent characteristics of this semisynthetic cephamycin and indicates that it should be a very valuable agent for treatment of bacterial infections.

Animals↗