Vincent P. Marshall

Marcfortine and Paraherquamide Class of Anthelmintics: Discovery of PNU- 141962

Three distinct chemical classes for the control of gastrointestinal nematodes are available: benzimidazoles, imidazothiazoles, and macrocyclic lactones. The relentless development of drug resistance has severely limited the usefulness of such drugs and the search for a new class of compounds preferably with a different mode of action is an important endeavor. Marcfortine A (1), a metabolite of Penicillium roqueforti, is structurally related to paraherquamide A (2), originally isolated from Penicillium paraherquei. Chemically the two compounds differ only in one ring; in marcfortine A, ring G is six-membered and carries no substituents, while in paraherquamide A, ring G is five-membered with methyl and hydroxyl substituents at C14. Paraherquamide A (2) is superior to marcfortine A as a nematocide. 2-Desoxoparaherquamide A (PNU-141962, 53) has excellent nematocidal activity, a superior safely profile, and is the first semi-synthetic member of this totally new class of nematocides that is a legitimate candidate for development. This review describes the chemistry, efficacy and mode of action of PNU-141962.

The effect of neutral resins on the fermentation production of rubradirin

SummaryRubradirin is an antibiotic of complex chemical structure which is activevs. methicillin resistant staphylococci. Its development has been limited due to inadequate production yields. The incorporation of neutral resins into fermentations ofStreptomyces achromogenes v.rubradiris, UC® 8051 resulted in the enhanced production of rubradirin. Resins HP-20, HP-21, XAD-2, XAD-7 and XAD-16 were employed in flask and tank fermentations. The incorporation of these resins promoted 2- to 4-fold enhancements of the rubradirin activity produced in flask fermentations, and the incorporation of XAD-16 and HP-21 into tank fermentations promoted production titer increases >5 fold.

Partial purification and characterization of a bacterial enzyme catalyzing reductive cleavage of anthracycline glycosides

Abstract A bacterial enzyme catalyzing the NADH-dependent reductive cleavage of certain anthracycline glycosides has been partially purified. The enzyme is acidic, stable in solution and has an estimated molecular weight of 35,000. The enzyme activity is strongly inhibited by molecular oxygen but not by cyanide or EDTA. No evidence has been found for an enzyme system or associated elements of electron transport.

Purification of macrolide 2′-phosphotransferase fromStreptomyces coelicolor Müller

SummaryAn enzyme that catalyzes 2′-O-phosphorylation of oleandomycin and several other macrolide antibiotics has been purified approximately 47-fold from cell-free extracts ofStreptomyces coelicolor Müller, NRRL 3532 (UC™ 5240). The reaction product was verified as being oleandomycin-2′-O-phosphate by mass spectrometry. As a result of purification, the enzyme was separated from two lincosaminide inactivating enzyme activities also present in the cell-free extract.

Effects of trospectomycin on serum sensitivity of Escherichia coli UC 9451.

Trospectomycin sulfate, a chemically synthesized analog of spectinomycin, exhibits a broad range of activity against both aerobes and anaerobes, including the etiological agents of sexually transmitted diseases. Its activity in vitro against Escherichia coli is considered only moderate. At subinhibitory levels, however, trospectomycin induced changes in a pathogenic strain of E. coli, UC 9451, which significantly increased its sensitivity to serum lysis. This strain of E. coli shows high-level resistance to serum in vitro, typically growing twofold within a 45-min incubation period. Following exposure to one-fifth the MIC of trospectomycin, greater than 99% of the bacteria were killed in 25% serum within 15 min. Surviving bacteria were static in this level of serum for over 3 h. Killing was due to lysis mediated by both the classical and alternative complement pathways. The bacteria exposed to trospectomycin were enlarged in both diameter and length, but they still grew at rates comparable to those of untreated bacteria. No other visible morphological changes could be directly related to the increase in serum sensitivity. The profile of outer membrane proteins obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was identical for trospectomycin-treated or untreated bacteria. However, the relative proportion of four major outer membrane proteins varied considerably. Images

Enzymic nucleotidylylation of lincosaminide antibiotics

SummaryFermentations ofStreptomyces coelicolor are known to convert lincosaminide antibiotics to mixtures of their inactive 3-(5′-ribonucleotides). In the present study, lincomycin, clindamycin and pirlimycin were nucleotidylylated and inactivated using crude enzyme preparations ofS. coelicolor. Optimal conversion is known to occur near pH 6 and to require Mg2+ and nucleoside 5′-triphosphates. In descending order of activity, inosine, adenosine, guanosine, cytidine and uridine 5′-triphosphates functioned as cofactors in these nucleotidylylations. In all instances, 90% of maximal conversion occurred within 24 h. When reaction rates were investigated as functions of enzyme protein addition, pirlimycin appeared to be the superior lincosaminide substrate. Antibiotic activities of these inactivation products could be regenerated through the action of phosphodiesterase, EC 3.1.4.1.