Biosynthesis of daunorubicin glycosides: role of epsilon-rhodomycinone

Abstract

Daunorubicin (daunomycin; NSC 82151) is a fermentation-derived anthracycline antibiotic that is clinically useful in the treatment of human leukemias. Daunorubicin itself is found rarely in microbial fermentations, but is present normally in the form of glycoside derivatives that yield the free drug on simple acid hydrolysis. A major by-product of daunorubicin fermentations is usually the structurally related anthracycinone e-rhodomycinone. We have used mutants of a daunorubicin-producing Streptomyces species to study the biosynthetic relationship between E-rhodomycinone and daunorubicin. We found that exogenously added E-rhodomycinone can be converted to daunorubicin glycosides by a nonproducing mutant and by a mutant that produces daunorubicin glycosides but not E-rhodomycinone. Molar conversion efficiencies were in the 15 to 30% range.The latter mutant was also shown to convert exogenous "C-labeled E-rhodomycinone to "C-labeled daunorubicin glycosides, again at conversion effitiencies of about 25%. The same biotransformation was observed with daunorubicin production strain C5, which normally accumulates both E-rhodomycinone and daunorubicin glycosides. A significant percentage (16 to 37%) of exogenously added e-['4C]rhodomycinonewas metabolized by strain C5, and 22 to 32% of the metabolized radioactivity could be recovered as daunorubicin glycosides. A mathematical model of E-rhodomycinone metabolism was constructed based on plausible assumptions concerning the kinetics of E-rhodomycinone accumulation and catabolism. When analyzed according to this model, our data indicate that most (63 to 73%), but not all, of the daunorubicin glycosides accumulated in the experiments with production strain C5 derived from e-rhodomycinone. A pathway network for the biosynthesis of daunorubicin glycosides is proposed that is in agreement with these data. In this proposed pathway network, e-rhodomycinone is an intermediate in one of at least two pathways which yield daunorubicin glycosides.Daunorubicin (Fig. 1) is an anthracycline antibiotic that is elaborated by several Streptomyces species

Biosynthesis of anthracyclines: carminomycin 4-O-methyltransferase, the terminal enzymic step in the formation of daunomycin

“…1). The enzymic reactions leading to the formation of c-rhodomycinone, an important intermediate in the biosynthesis of daunomycin (McGuire et al, 1980;Strohl et af., 1989), have recently been clarified (Eckardt & Wagner, 1988;Connors et al, 1990). On the other hand, the biosynthetic steps required to convert E-rhodomycinone to daunomycin are virtually uncharacterized, although it is obvious that the following reactions must take place: (i) decarbomethoxylation at C-10; (ii) twostep oxidation from a methylene to a keto group at C-13 ; (iii) 0-methylation of the C-4 hydroxyl group; and (iv) glycosylation with daunosamine of the C-7 hydroxyl group (Strohl et al, 1989).…”

“…strain C5, which produces erhodomycinone and baumycins (anthracyclines related to daunomycin; McGuire et al, 1980), was obtained from the Frederick Cancer Research Center. Streptomyces galilaeus (ATCC 3 1 133), which produces aclacinomycin A (Oki et al, 1979), and the daunomycin producing strains Streptomyces peucetius (ATCC 29050), Streptomyces coeruleorubidus (ATCC 31276) and Streptomyces insignis (ATCC 31913; Tunac et al, 1985) were obtained from the American Type Culture Collection.…”

Isolation and characterization of a gene from Streptomyces sp. strain C5 that confers the ability to convert daunomycin to doxorubicin on Streptomyces lividans TK24

“…strain C5 produces daunomycin and baumycins (23,24). In the 10 years that we have studied daunomycin biosynthesis by this strain (4-7, 13, 14, 31, 32, 37), we have never observed it to produce doxorubicin.…”

Partial purification and properties of carminomycin 4-O-methyltransferase from Streptomyces sp. strain C5

“…strain C5 fermentations, very little daunomycin is actually produced ; E-rhodomycinone, a known intermediate, is the major metabolite accumulated (McGuire et al, 1980;Bartel et al, 1990). The fact that CMT activity in crude cell extracts is below the limits of detection correlates with the low daunomycin titres obtained.…”

“…The KA values for carminomycin and 13-dihydrocarminomycin seem to reflect accurately the low concentrations of daunomycin produced by Streptomyces sp. strain C5 (McGuire et al, 1980;Bartel et al, 1990).…”