ABSTRACT
1. delta-(L-alpha-Amino[4,5-3H]adipyl)-L-cysteinyl-D-[4,4-3H]valine has been synthesized from its constituent amino acids, the L-alpha-amino[4,5-3H]adipic acid being obtained by reduction with 3H2 of methyl 5-acetamido-5,5-diethoxycarbonylpent-2-enoate and subsequent decarboxylation and hydrolysis. 2. In a cell-free system prepared by lysis of protoplasts of Cephalosporium acremonium 3H was incorporated from the doubly labelled tripeptide into a compound that behaved like penicillin N or isopenicillin N. The relative specific radioactivities of the alpha-aminoadipyl and penicillamine moieties of the penicillin were the same (within experimental error) as those of the alpha-aminoadipic acid and valine residues respectively of the tripeptide. 3. The behaviour of the labelled alpha-aminoadipic acid from the penicillin to the L-amino acid oxidase of Crotalus adamanteus venom showed that it was mainly L-alpha-aminoadipic acid. 4. The results are consistent with the hypothesis that the carbon skeleton of the LLD-tripeptide is incorporated intact into the penicillin molecule and that the first product is isopenicillin N.
Subject(s)
Oligopeptides/metabolism , Penicillins/biosynthesis , 2-Aminoadipic Acid/metabolism , Acremonium/metabolism , Amino Acid Oxidoreductases/metabolism , Isomerism , Oligopeptides/chemical synthesis , TritiumABSTRACT
1. The stereoisomers of delta-(alpha-aminoadipyl)-L-cysteinylvaline (LLD, LLL and DLD) were synthesized from valine labelled with 3H in its methyl groups or in the alpha position. L-Cysteinyl-D-[4,4'-3H]valine was also synthesized. 2. 3H was incorporated into a compound that behaved like penicillin N when the LLD tripeptide containing either a methyl- or an alpha-labelled valine residue was incubated with a cell-free system prepared by lysis of protoplasts of Cephalosporium acremonium. 3. Incorporation was not observed under these conditions from the labelled all-L- or DLD-tripeptide, from L-cysteinyl-D-[4,4'-3H]valine, or of Penicillium chrysogenum appeared to be the LLD isomer, like that from C. acremonium. 5. These findings are discussed in relation to penicillin biosynthesis.
Subject(s)
Oligopeptides/chemical synthesis , Penicillins/biosynthesis , Acremonium/metabolism , Cell-Free System , Cysteine , Dipeptides/chemical synthesis , Penicillium chrysogenum/metabolism , Protoplasts , Stereoisomerism , Tritium , Valine/chemical synthesisABSTRACT
Poly (3'-O-carboxymethyl-2'-deoxyctidine) (VII) has been synthesised by the polymerisation of 3'-O-carboxymethyl-4-N-phenoxyacety-2'-deoxycytidine (V) and removal of the phenoxyacetyl groups under acidic conditions. V was obtained by the action of 2,4-dinitrophenyl phenylacetate on 3'-O-carboxymethyl-5'-O-triphenylmethyl-2'-deoxycytidine (III) followed by removal of the triphenylmethyl group under carefully controlled acidic conditions. The polymer, VII gave a hypochromic effect of about 20% at 250nm when mixed with poly (1) in 0.2Macetate, pH 5.0. It appeared, therefore, that a complex was formed. Upon heating a solution of this complex there was an initial decrease in optical density followed by a much larger increase to give a Tm of about 60 degrees. Attempts to form the 3'-O-carboxymethyl derivative of 4-N-phenoxyacetyl-5'-O-'triphenylmethyl-2'-deoxycytidine to give a shorter synthetic route to VII were not successful. 3'-O-Carboxymethyl-2'-deoxycytidine was obtained by removal of thetriphenylmethyl group from III. Attempts to polymerise this compound in concentrated aqueous solution with a water-soluble carbodiimide were not successful.
