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Research has been conducted on the biotransformation of crotonobetaine to L-carnitine in Escherichia coli. The catalysis of this reversible biotransformation carried out by CaiB and CaiD proteins in the presence of a cosubstrate has been investigated and described.

The expression, purification and characterization of the enzyme methane monooxygenase (sMMO) and the complete 16S rDNA and sMMO sequencing of isolate WI14 were studied. The sMMO revealed a very narrow substrate specificity and oxidizes some aliphatics, aromatics and halogenated compounds only to their corresponding hydroxylated products. The 16S rDNA sequencing and comparison with that of other known methanotrophic bacteria confirmed that strain WI 14 is very close to the genus Methylocystis.

The stereochemical course of the hydration of trans-crotonobetaine to L-(-)-carnitine by the L-carnitine dehydratase enzyme was determined using single-crystal neutron diffraction. X-ray analysis of ((Chsub3)sub3N-Chsub2-CH(OH)-CHsub2-COOH)+(AuC1sub4)-, an undeuterated carnitinium salt, confirmed the configuration of L-(-)-carnitine at the Csub3 position. Neutron analysis showed that the CHD group had the absolute R configuration at position Csub2.

The open reading frame of 393 bp called caiF in Escherichia coli which is located before the caiTABCDE operons is identified and examined. The caiF gene encodes a protein composed of 131 amino acids with a molecular mass of 15,438 Da. The start site of transcription is at position 82 after the caiF initiation codon. Overexpression of CaiF initiated the transcription of the divergent cai and fix operons in the presence of carnitine.

The caiB gene that encodes carnitine dehydratase consists of a 405 amino acid polypeptide and is 1,215 bp long. The N-terminal sequence of the gene is identical to that of the predicted gene sequence. Cotranscription of the gene with another gene is revealed by northern RNA analysis. The other gene is identified to encode a 47-kDa protein in the upstream of the CaiB gene.

An extracellularly exported beta-lactamase from Acinetobacter calcoacteticus CCM 5593 was purified and characterized. The key step towards purification was affinity chromatography on m-amino-phenyl-boronic-acid-hemisulphate modified Affi-Gel 10, resulting in a 430-fold purified enzyme. Characterization experiments showed that the beta-lactamase hydrolyzes cephalosporins better than penicillins. Furthermore, it is inhibited by cloxacillin, carbenicillin, penicillic acid sulphone and aztreonam. These results indicate that the extracellular beta-lactamase produced by A. calcoaceticus CCM 5593 is a typical cephalosporinase.