Biosynthesis of formycin. Incorporation and distribution of labeled compounds into formycin.

Abstract

1. Two carbons, carbon-2 and one of carbons-3 to -5, of lysine seemed likely to be incorporated into one of carbon of the chromophore moiety of formycin.2. From the results of radioisotopic studies with glutamate, r-amino-n-butyrate or organic acids related to tricarboxylic acid cycle, the important role of glutamate in the biosynthesis of formycin was strongly suggested.3. The incorporation of nitrogen(s) of lysine into three nitrogens, including two nitrogens of pyrazole ring, of formycin was suggested by mass spectroscopy. 4. Ribose was estimated as a direct precursor for the ribosyl moiety of formycin, whereas the biosynthesis of ribose was shown to occur via the pathway other than hexose monophosphate shunt or glucuronate pathway.5. In replacement culture, the salvage synthesis of formycin from its chromophore moiety was not observed and it was also evident that the chromophore moiety or pyrazofurin (pyrazomycin) inhibited the biosynthesis of formycin.There have been several investigations on the biosynthesis of C-riboside nucleosides, i.e., pseudouridine, showdomycin, minimycin, pyrazofurin (pyrazomycin) and the formycin family. In the biosynthesis of pseudouridine, the intramolecular rearrangement in tRNA of uridylate to pseudouridylate has been strongly suggested.1-6) The biosynthesis of showdomycin has been well established and confirmed to occur by the condensation of ribose and an asymmetric four-carbon dicaboxylic acid.7-10)Recently, studies on the biosynthesis of minimycin revealed a novel mechanism whereby C-riboside linkage is formed from sedoheptulose 7-phosphate (or eight-carbon branched chain sugar phosphate).11) C-Riboside linkage of pyrazofurin was also believed to be formed by this mechanism.11)The biosynthesis of formycin by Nocardia interforma has been proposed to occur via a pathway other than that of biosynthesis of purine nucleotide while exogeneously added ribose was estimated to be incorporated into the ribosyl moiety of formycin.12) It was also reported that formycin may be formed from formycin 5'-monophosphate then deaminated to formycin B.13) Using Streptomyces sp.MA406-A-1, a formycin-producing strain, we reported that carbon atom from lysine, glutamate and/or aspartate was incorporated into formycin with high efficiency, and that novel enzyme(s) catalyzing the amination of formycin B to formycin was present in this organism. 14,15) To elucidate the more detailed mechanism of formycin biosynthesis, we examined the incorporation and the distribution of various labeled compounds into formycin and this paper presents the results of these studies.

Occurrence of the Stringent Response in Streptomyces sp. and its Significance for the Initiation of Morphological and Physiological Differentiation

“…In B. subtilis the decrease of intracellular GTP, caused by the stringent response (or more directly by the inhibitors of GMP synthesis), results in an initiation of sporulation (Lopez et al, 1981 ;Ochi et al, 1981Ochi et al, , 1982. Aerial mycelium formation of Streptomyces has also been shown to be initiated by the addition of decoyinine (a specific inhibitor of GMP synthesis), which caused a decrease in the pool of GTP (Ochi, 1986).…”

“…1) A small amount of chloramphenicol (0.7 pg mF1, added just after inoculation) reduced formycin production by 65 % without affecting growth. Since chloramphenicol inhibits ppGpp synthesis in B. subtilis (Ochi & Freese, 1983), these results raised the possibility that ppGpp is the physiological initiator of formycin production. To assess this possibility, I isolated relaxed (re0 mutants which might lack the ability to produce ppGpp.…”

“…Low levels of chloramphenicol inhibit the synthesis of both ppGpp and pppGpp without affecting cell growth of B. subtilis (Ochi & Freese, 1983). With Streptomyces sp., low levels of chloramphenicol(2 pg ml-l ) similarly blocked accumulation of ppGpp induced by deprivation of Casamino acids (compare Fig.…”

A Decrease in GTP Content is Associated with Aerial Mycelium Formation in Streptomyces MA406-A-1

“…This is of interest because sporulation of Bacillus suhtilis (an endospore-forming bacterium) has been shown to be triggered by a partial decrease of the G T P pool in the presence of excess carbon, nitrogen and phosphate sources (Lopez cjt al., 1979;Freese, 1981 ; Ochi t't a/., 198 1). As in B. suhtilis, a decrease in the pool of G T P (or some closely related molecule) may be a sufficient signal for the initiation of aerial mycelium formation of Streptoniyces.…”

“…also produce numerous antibiotics; this production is usually coupled to morphological differentiation (Chater, 1984;Chater & Hopwood, 1984). In Bucillus suhtilis, the decrease of intracellular G T P (or GDP) content caused by the stringent response or more directly by inhibitors of G M P synthesis, results in an initiation of sporulation (Lopez et d., 1979;Freese, 1981 ;Ochi et a/., 1981 ;Ochi & Freese, 1983). Freese et ul.…”