Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme's original classification as EC 4.2.1.16, threonine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond [3,5]. The latter reaction, which can occur spontaneously, is also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase . The enzymes from a number of sources also act on L-serine, cf. EC 4.3.1.17, L-serine ammonia-lyase.
Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme's original classification as EC 4.2.1.16, threonine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond [3,5]. The latter reaction, which can occur spontaneously, is also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase [5]. The enzymes from a number of sources also act on L-serine, cf. EC 4.3.1.17, L-serine ammonia-lyase.
native enzyme is totally inhibited by 15 mM Ile, the heterologous catabolic enzyme from E. coli retains 60% of its original activity even in presence of 200 mM Ile
production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from a single unrelated carbon source via threonine biosynthesis in Escherichia coli, by overexpression of threonine deaminase, which is the key factor for providing propionyl-coenzyme A (propionyl-CoA), from different host bacteria, removal of the feedback inhibition of threonine by mutating and overexpressing the thrABC operon in Escherichia coli, and knock-out of the competitive pathways of catalytic conversion of propionyl-CoA to 3-hydroxyvaleryl-CoA. Construction of a series of strains and mutants leads to production of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer with differing monomer compositions in a modified M9 medium supplemented with 20 g/liter xylose. The largest 3-hydroxyvalerate fraction obtained in the copolymer is 17.5 mol%