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The synthesis of two cyclopropyl-containing tripeptide analogues designed as probes for the mechanism of isopenicillin N synthase is described. Findings reveal that key differences were found to exist in substrate orientation and water occupancy, which allow for an explanation of the differences in reactivity of these substrates.

The biomimetic synthesis of the bioesquiterpene lactones (plus or minus)-biatractylolide and (plus or minus)-biepiasterolide via dimerization of the captodative stabilized radical is reported. Atractylon is also observed as a possible intermediate during the biosynthesis of biatractylolide, biepiasterolide, atractilolide, and hydroxyatractylolide.

Research points out that in the taurine/alpha-ketoglutarate dioxygenase and the 2,4-dichlorophenoxyacetate/alphaketoglutarate dioxygenase enzymes, the iron center is proximal to the residues undergoing post-translational modifications. Data indicate that the former enzyme selects a tetrahedral substrate anion, while the latter prefers planar carboxylate, suggesting differences in the catalysis mediated by the enzymes.

Research has been conducted on the kainoid amino acids possessing an unnatural substituents at C-4. The rule of assigning C-4 stereochemistry to the C-4 epimers used for the protected and unprotected kainoids is described.

Research has been conducted on the heteroaromatic acromelic acid analogues. The synthesis of these analogues carried out in a parallel fashion from (-)-alpha-kainic acid is described.

Research has been conducted on the biotin and lipoate synthases. The results of Mossbauer studies of (super)57 Fe-reconstituted biotin synthase are presented.

Research involving the direct oxygenation of anaerobically grown crystals of isopenicillin N synthase, a non-haem iron-dependent oxidase, complexed with Fe2+ and substrates, then structural analysis by X-ray crystallography, supports the hypothesis of a two-stage reaction sequence leading to penicillin. The most simple explanation for the formation of a monocyclic sulphoxide product from delta-(L-alpha-aminoadipoyl)-L-cysteinyl-L-S-methylcysteine is the interception of a high-valency iron-oxo species.

Penicillins and cephalosporins are widely used antibiotics derived from a fermentation process because their commercial synthesis is too expensive. The enzyme involved in the biosynthesis of eukaryotic cephalosporins is a 2-oxyglutarate-dependent ferrous enzyme, DAOCS (deacetoxycephalosporin C synthase), which catalyses the expansion of the bicyclic penicillin core into cephalosporin. New research describes the three crystal structures for prokaryotic DAOCS from Streptomcyes clavuligerus, the enzyme complexed with FE(II) and with FE(II) and 2-oxoglutarate. A mechanism for ferryl formation is suggested.

Peptidic and nonpeptidic trifluoromethyl ketones were synthesized by reacting (trifluoromethyl)trimethylsilane with oxazolidin-5-ones. Moderate acid hydrolysis of adducts with electron-releasing substituents at C-2 resulted in N-substituted alpha-amino trifluoromethyl ketones (TFMKs). N-CBZ-protected alpha-amino TFMKs were transformed into hydrochloride salts of alpha-amino TFMKs via hydrogenolysis.

The iron ligands of 1-aminocyclopropane-1-carboxylate (ACC) oxidase were identified and the functional consequences of altering them for catalysis and oxidative modification were observed. Findings are in good agreement with the predictions that H177, D179 and H234 act as metal ligands during catalysis. Also, H234 does not ligate to the iron during fragmentation of the wild-type enzyme, indicating that active site directed oxidative inactivation is due to improper metal binding.

Many new antibiotics have been developed but penicillins and cephalosporins still have considerable clinical use. Extensive studies have revealed a clear picture of the enzyme catalyzed steps involved in the biosynthesis of penicillins and cephalosporins. The initial step in the biosynthesis of penicillin, involves the biosynthesis of L-sigma-(alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). The reactions catalyzed by ACV synthetase and its primary structure are discussed.

The timing of the loss of the (super)18 O label from di[(super)18]valine in both dipeptide products L-O-(methylserinyl)-L-valine and L-O-(methylserinyl)-D-valine was investigated. Results have demonstrated that the formation of the peptide bond between L-valine and L-O-methylserine occurs prior to any formation of a covalent thioesther bond to the valine carboxyl group.

Research suggests that penicillin can be formed using a crystal structure of the iron-dependent non-haem oxidase isopenicillin N synthase. The structure is complexed to ACV and ferrous iron with a resolution of 1.3 Angstrom. Dioxygen can bind into the vacant iron coordination site formed by the ligation of ACV to the structure's iron centre. Hydrogens are removed from ACV by iron-oxo and iron-dioxygen species with no aid from protein residues.

The inactivation of 1-aminocyclopropane-1-carboxylate (ACC) oxidase has been investigated. The rates of inactivation of purified, recombinant ACC oxidase from tomato under different combinations of substrates and cofactors were measured. The results showed that ACC oxidase inactivates via slow partial unfolding of the catalytically active conformation, by oxidative damage from hydrogen peroxide solution and oxidative damage to the active site.

Isopenicillin N synthase (IPNS) complexed with manganese creates a new structural family of enzymes and may allow for the synthesis of penicillin once the structure has been analyzed. IPNS has homologous regions with 1-aminocyclopropane-1-carboxylic acid oxidase and 2-oxo-acid-dependent oxygenase, all of which have a jelly-roll motif. The manganese ion takes the place of ferrous ion at the metal binding site and allows for the catalysis of many oxidative chemical processes such as desaturation, hydroxylation and cyclization.