title: Molecular characterization of the genes encoding acetohydroxy acid synthase in the cyanobacterium Spirulina platensis.
abstract: The enzyme acetohydroxy acid synthase (AHS), which catalyses the first common step in the biosynthesis of isoleucine, leucine and valine, has been demonstrated to be present in Spirulina platensis in two isoenzymic forms. The complete nucleotide sequences of the genes ilvX and ilvW encoding these two enzymes have been determined. Sequence analysis revealed the presence of two open reading frames, of 1836 and 1737 nucleotides for ilvX and ilvW, respectively. The predicted amino acid sequences of the two isoenzymes, compared with the Synechococcus PCC 7942 AHS enzyme and the large subunits of the Escherichia coli AHSI, II, III isoenzymes, revealed a notable degree of similarity. A small subunit has not been identified for either of the S. platensis AHS isoenzymes. Analysis by Northern blot hybridization demonstrated that the ilvX and ilvW genes are transcribed to give mRNA species of approximately 2.15 kb and 1.95 kb, respectively.
authors.affiliation: Dipartimento di Genetica e Microbiologia A. Buzzati Traverso, Pavia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Milano
authors.forename: E
authors.initials: E
authors.lastname: De Rossi
authors.forename: E
authors.initials: E
authors.lastname: Zanaria
authors.forename: L
authors.initials: L
authors.lastname: Barbierato
authors.forename: O
authors.initials: O
authors.lastname: Ciferri
authors.forename: G
authors.initials: G
authors.lastname: Riccardi
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics*; D004269:DNA, Bacterial; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D000095:Acetolactate Synthase