5923-DNI, a new deoxyribonuclease inhibitor produced by Streptomyces sp. strain No. A-5923

[Metabolites produced by actinomycetes--antiviral antibiotics and enzyme inhibitors]

In 1995, we discovered new antiherpetic antibiotics, called fattiviracins. The producing organism was classified as a strain belonging to Streptomyces microflavus. The strain produced at least 13 fattiviracin derivatives (FV-1 to FV-13). Fattiviracins were obtained as a white amorphous powder, and their molecular weights are in the range of 1400 to 1500. They are readily soluble in water, methanol, pyridine, and DMSO, but insoluble in other organic solvents. Fattiviracins have macrocyclic diesters formed by the binding of two trihydroxy fatty acids and two D-glucose residues in the molecule, and they can be divided into five families according to the length of the fatty acid moiety. Fattiviracins have potent activity against enveloped DNA viruses such as the herpes family, HSV-1, and VZV and enveloped RNA viruses such as influenza A and B viruses, and three strains of HIV-1, with EC(50) values on the order of a few micrograms per milliliter. The biosynthetic pathway of fattiviracins is also becoming clearer. Using bacitracin-resistant strains, enhanced and astringent production of fattiviracin was achieved. Fattiviracin FV-13, which has the longest fatty acid chains in the molecule, was dramatically enhanced by a C(55)-isoprenyl phosphate metabolism. In addition, we have screened various inhibitors of enzymes such as alkaline protease, glucosyltransferase, glucuronidase, phospholipase, deoxyribonuclease, DNA methyltransferase, and DNA topoisomerase. All the inhibitors we discovered are briefly summarized in this paper.

Deoxyribonuclease inhibitors produced by streptomycetes

Streptomyces sp. strain No. A-5838 produces three types of inhibitors of DNase II. Two of them, DNI-2 and DNI-3, were distinguished from the previously reported DNase II inhibitors, 5838-DNI and 5923-DNI, by their inhibitory profiles towards phosphodiesterases. DNI-2 has M(r) 654, and is considered to be a coproporphyrin. DNI-3 is an acidic substance with M(r) about 60,000 as estimated by gel filtration. The inhibitory activities of both inhibitors were shown to be temperature-dependent whereas only that of DNI-2 was pH-dependent.

5838-DNI, a deoxyribonuclease inhibitor produced by Streptomyces sp. strain no. A-5838

5838-DNI, an inhibitor of deoxyribonuclease (DNase) II from porcine spleen was produced by Streptomyces sp. strain No. A-5838. The structure of 5838-DNI was shown to be 1,4,4a,5,12,12a-hexahydro-4,4a,11,12a-tetrahydroxy-3,8-dimethoxy-9- methoxycarbonyl-10-methyl-1,5,12-trioxo naphthacene. Although similar in structure to tetracenomycin C, which is an antibiotic against Gram-positive bacteria, 5838-DNI has different antibacterial activity. 5838-DNI was distinguished from 5923-DNI, a previously reported DNase II inhibitor, in inhibitory activity against each enzyme. 5838-DNI showed dependency of inhibition on pH and temperature, and inhibited phosphodiesterase I in a competitive manner. These data suggest that 5838-DNI is the first reported example of an inhibitor of microbial origin which is able to inhibit DNase II and phosphodiesterase I.