The biosynthesis of penicillin. V. Comparison of valine and hydroxyvaline as penicillin precursors

Penicillin-induced formation of ribonuclease in rice (Oryza sativa L.) endosperm and its inhibition by abscisic acid

Penicillin stimulates the formation of ribonuclease in embryoless rice (Oryza sativa L.) endosperm and enhances gibberelin-induced response. Penicillin-induced RNase production is completely inhibited by abscisic acid.

The stereochemistry of beta-lactam formation in penicillin biosynthesis

1. (2R,3S)-[U-14C,3-3H1]- and (2R,3R)-[U-14C,2,3-3H2] Cysteine hydrochlorides have been separately synthesised. The latter compound has been shown to have uniform distributions of tritium between C-2 and C-3. 2. The abvoe cysteines and (2R)-[U-14C,3,3,3',3'-3H4]cystine have been converted to samples of penicillin G by Penicillium chrysogenum. 3. Incorporation results indicate that all but 14% of the tritium is lost from the (2R,3S)-[3-3H1]isomer; that 42% of tritium is retained by the non-stereospecifically C-3 tritiated cystine; and that 58% of tritium is retained by the (2R,3R)-[2,3-3H2]isomer on conversion to penicillin G. 4. Degradation of the penicillin G derived from (2R,3R)-[U-14C,2,3-3H2]cysteine hydrochloride has indicated that in fact about 87% of the original C-3 tritium of cysteine is retained at C-5 of penicillin G. 5. The results indicate stereospecificity in the cyclisation giving rise to the beta-lactam ring in penicillin G in nature with loss of the 3-pro-S-hydrogen and rentention of the 3-pro-R-hydrogen of cysteine. Thus there is net retention of stereochemistry in the cyclisation.

Deoxyribonucleic acid-induced anomalous optical rotatory dispersion of antimalarial drugs and dyes

l-[3,3′-³H]cystine was incorporated into penicillin with retention of one tritium. This result can be explained by β-lactam formation through ring closure between C3 of cysteine and NH of valine. No radioactivity of dl-[2,3-³H]valine was incorporated into penicillin. The loss of isotope at C2 occurs during the inversion of configuration. The loss of label at C3 is discussed in terms of possible intermediates for the formation of the thiazolidine ring of penicillin.