Chorismate mutase catalyzes the conversion of chorismate to prephenate that is the first committed step in the biosynthesis of the aromatic amino acids phenylalanine and tyrosine. A chorismate mutase gene, designated SmCM1, was isolated from Salvia miltiorrhiza by using RT-PCR. The full length of SmCM1 cDNA consists of 948 nucleotides and has an open reading frame of 765 bp. The deduced amino acid sequence of SmCM1 has 255 amino acid residues which forms a 36.0 kD polypeptide with calculated pI of 6.41 as expected. The putative polypeptide contains a CM_2 super family function domain. Blast W results showed that SmCM1 had 70% of the similarity with Petunia x hybrid CM, 72% of the similarity with Arabidopsis thaliana CM, and 64% of similarity with Populus trichocarpa CM. The transcription level of SmCM1 in root, stem and leaf was analysed by realtime quantitative PCR. The results showed the expression level of the SmCM1 in leaf was highest, and lowest in root. Yeast extract and silver ion joint induction could markedly stimulate the increase of mRNA expression of SmCM1 and its upstream 3-deoxy-7- phosphoheptulonate synthase (DAHPS) and chorismate synthase (CS). It was 7.9, 5.5 and 9.8 times of control on 8 h after induction, respectively.
Amino Acid Sequence ; Chorismate Mutase ; chemistry ; genetics ; metabolism ; Cloning, Molecular ; Molecular Sequence Data ; Phylogeny ; Plant Proteins ; chemistry ; genetics ; metabolism ; Protein Structure, Tertiary ; Salvia miltiorrhiza ; chemistry ; classification ; enzymology ; genetics

The aspartate kinase (AK) from Mycobacterium tuberculosis (Mtb) catalyzes the biosynthesis of aspartate family amino acids, including lysine, threonine, isoleucine and methionine. We determined the crystal structures of the regulatory subunit of aspartate kinase from Mtb alone (referred to as MtbAKβ) and in complex with threonine (referred to as MtbAKβ-Thr) at resolutions of 2.6 Å and 2.0 Å, respectively. MtbAKβ is composed of two perpendicular non-equivalent ACT domains [aspartate kinase, chorismate mutase, and TyrA (prephenate dehydrogenase)] per monomer. Each ACT domain contains two α helices and four antiparallel β strands. The structure of MtbAKβ shares high similarity with the regulatory subunit of the aspartate kinase from Corynebacterium glutamicum (referred to as CgAKβ), suggesting similar regulatory mechanisms. Biochemical assays in our study showed that MtbAK is inhibited by threonine. Based on crystal structure analysis, we discuss the regulatory mechanism of MtbAK.
Amino Acid Sequence ; Aspartate Kinase ; chemistry ; genetics ; metabolism ; Binding Sites ; Cloning, Molecular ; Corynebacterium glutamicum ; enzymology ; Crystallization ; methods ; Crystallography, X-Ray ; Enzyme Activation ; Enzyme Assays ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; metabolism ; Lysine ; pharmacology ; Molecular Sequence Data ; Mycobacterium tuberculosis ; drug effects ; enzymology ; Plasmids ; genetics ; metabolism ; Prephenate Dehydrogenase ; metabolism ; Protein Structure, Secondary ; Threonine ; metabolism ; pharmacology