Occurrence and biosynthesis of C-demethylactinomycins in actinomycin-producing Streptomyces chrysomallus and Streptomyces parvulus

Abstract

Streptomyces chrysomallus and Streptomyces parvulus produce novel C-demethylactinomycins besides their normal actinomycins when fed with 3-hydroxyanthranilic acid (3-HA). The 3-HA is incorporated into pentapeptide lactone precursors in competition with the regular precursor 4-methyl-3-hydroxyanthranilic acid (4-MHA). The resultant 3-HA pentapeptide lactones can condense with each other, as well as with the continuously formed 4-MHA pentapeptide lactones giving C-demethylactinomycins lacking one or both methyl groups in their phenoxazinone chromophores. In case of C-demethylactinomyins lacking one methyl group, the condensation was shown to be regiospecific directing the 3-HA portion almost exclusively to the α-side of the phenoxazinone chromophore. As 3-HA is a weaker substrate for the 4-MHA-incorporating enzyme actinomycin synthetase I than 4-MHA, C-demethylactinomycins never exceeded 7-8% of total actinomycin formed. Surprisingly, C-demethylactinomycins (up to 0.8%) were also found in the actinomycin mixtures of unsupplemented streptomycete cultures after longer cultivation times, indicating the natural presence of 3-HA. Feeding with 3-hydroxykynurenine (3-HK) induced also formation of C-demethylactinomycins indicating that 3-HK is source of 3-HA. Analysis of tryptophan metabolites in the intracellular pools of the streptomycetes using 5-(3)H-tryptophan as radiotracer revealed formation of 4-MHA, but not of 3-HA. This indicates that intracellular 3-HK is almost exclusively converted to 3-hydroxy-4-methylkynurenine (4-MHK), which has been identified previously as direct precursor of 4-MHA. However, small amount of 3-HK leaking out from the 4-MHA pathway can be prematurely converted to 3-HA all along the cultivation of the streptomycetes resulting in the formation of natural C-demethylactinomycins.

Investigation of antibacterial and anti-cancer activities of Streptomyces sp SRF1 culture filtrate

“…It was recently reported that 70 % of all antibiotics in use were derived from actinomycetes bacteria [2], 75 % of these from the genus Streptomyces [4][5][6]. Antibiotics derived from Streptomyces have antibacterial, antifungal, antioxidant, and antitumor activities [7][8][9][10][11].…”

Neo-actinomycins A and B, natural actinomycins bearing the 5H-oxazolo[4,5-b]phenoxazine chromophore, from the marine-derived Streptomyces sp. IMB094

“…Natural actinomycins differ in amino acid composition of the peptidolactone side chains, whereas the chromophore (2-amino-4,6-dimethylphenoxazine-3-one-1,9-dicarboxylic acid, actinocin) is identical in all reported actinomycins 2 . Recently, S. chrysomallus and S. parvulus were reported to generate new C-demethylactinomycins lacking one or both methyl groups in their phenoxazinone chromophores when cultured with 3-hydroxyanthranilic acid 5 .…”

Blood cells serve as a source of factor‐inducing rapid ischemic tolerance in brain

“…The calculated mass of actinomycin was 1255.42 Da. The major peak detected in plasma samples was sodium adduct of ActD [M + Na] + , which exhibits a mass peak at m/z 1277.25 (Crnovcic et al, 2013).…”