The metC gene of Escherichia coli K-12 was cloned and the nucleotide sequence of the metC gene and its flanking regions was determined. The translation initiation codon was identified by sequencing the NH2-terminal part of 13-cystathionase, the MetC gene product. The meIC gene (1185 nucleotides) encodes a protein having 395 amino acid residues.The 5' noncoding region was found to contain a "Met box" homologous to sequences suggestive of operator structures upstream from other methionine genes that are controlled by the product of the pleiotropic regulatory metJ gene. The deduced amino acid sequence of (3-cystathionase showed extensive homology with that of the MetB protein (cystathionine y-synthase) that catalyzes the preceding step in methionine biosynthesis. The homology strongly suggests that the structural genes for the MetB and MetC proteins evolved from a common ancestral gene.

In the Staphylococcus aureus strain harbouring the plasmid RPAL, the resistance to aminoglycoside antibiotics results from two inactivating reactions catalyzed by a 6′‐N‐aminoglycoside acetyltransferase and a 2”‐O‐aminoglycoside phosphotransferase. These enzymes are copurified with a constant ratio between the two activities, the purification process consisting in affinity chromatography, native electrophoresis and gel exclusion chromatography. The kinetic mechanisms of each activity have been determinated from studies of initial velocities, as well as product and dead‐end inhibitions. Both activities follow a random rapid equilibrium mechanism. The substrates and cofactors of one reaction have been tested as effectors of the other reaction. No interaction between the two activities has been observed. However, the GTP cofactor of phosphotransferase protects, at weak concentrations, the acetyltransferase against thermal inactivation, which suggests that the two activities may be associated.

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Covalent embedding of a (eta(6)-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water.