branched-chain amino acid aminotransferase
branched-chain amino acid-glutamate transaminase
L-branched chain amino acid aminotransferase
glutamate-branched-chain amino acid transaminase
This enzyme belongs to Type-VI PLP-dependent enzyme (see [3] & [5]). According to the literature [10], this enzyme catalyzes the following reactions. (A) Formation of external aldimine (with amine group of the first substrate, Leucine). (A1) The negative charges from phosphate group of PLP and alpha-carboxylate of the first substrate may deprotonate the nucleophile, the alpha-amino group of the substrate (see [10]). (A2) The activated alpha-amino group of the first substrate makes a nucleophilic attack on the C4' atom of PLP (from the si-face side), forming a tetrahedral intermediate. (A3) Probably, the lone pair of the substituted amino group makes another attack on the C4' atom of PLP (from the si-face side), releasing Lys159. This may facilitated by O3 atom of PLP and Tyr164, considering the structure (see [10]). (The O3 atom might act as a acid-base to transfer a proton from the amine group to sidechain of Lys159.) (B) Isomerization (change in the position of double-bond). (B1) Lys159 acts as a general base to deprotonate the alpha-proton of the substrate bound to PLP, forming the quinonoid intermediate. The activity of Lys159 must be modulated by Tyr164 & O3 atom of PLP. (B2) Lys159 acts as a general acid to protonate the C4' atom of the intermediate, forming the ketimine intermediate. (C) Schiff-base deforming (by hydration), releasing the first product, 2-oxo acid, and PMP. (C1) Lys159 acts as a general base to activate a water (at the re-face side of cofactor). (C2) The activated water molecule makes a nucleophilic attack on the C-alpha atom of the substrate (from the re-face side), forming a carbinolamine intermediate. (C3) The lone pair of the new hydroxyl group makes a nucleophilic attack on the C4' atom, releasing the first product. This reaction may facilitated by Tyr164 and the O3 atom of PLP. (The O3 atom might act as a base to deprotonate the sidechain of Lys159, which in turn deprotonate the hydroxyl group. The O3 atom then acts as a acid to protonate to the leaving amino group of the intermediate.) (D) Schiff-base forming (of PMP with carbonyl group of the second substrate, Oxoglutarate; by dehydration). (E) Isomerization (change in the position of double-bond). (F) Formation of internal aldimine, releasing the second product, Glutamate.
D-amino Acid Aminotransferase; Chain A, domain 2
D-amino Acid Aminotransferase; Chain A, domain 1
Valine, leucine and isoleucine degradation
Valine, leucine and isoleucine biosynthesis
Crystallization and preliminary X-ray characterization of branched-chain amino acid aminotransferase from Escherichia coli.
Crystal structures of branched-chain amino acid aminotransferase complexed with glutamate and glutarate: true reaction intermediate and double substrate recognition of the enzyme.
Three-dimensional structure of Escherichia coli branched-chain amino acid aminotransferase at 2.5 A resolution.
Structure, evolution and action of vitamin B6-dependent enzymes.
Branched-chain amino-acid aminotransferase of Escherichia coli.
The structure of human mitochondrial branched-chain aminotransferase.
Structures of Escherichia coli branched-chain amino acid aminotransferase and its complexes with 4-methylvalerate and 2-methylleucine: induced fit and substrate recognition of the enzyme.
Structure and function of branched chain aminotransferases.
Identification of a peroxide-sensitive redox switch at the CXXC motif in the human mitochondrial branched chain aminotransferase.
Crystal structures of human mitochondrial branched chain aminotransferase reaction intermediates: ketimine and pyridoxamine phosphate forms.