Kinetics and regulation of pantothenate kinase from Escherichia coli.

摘要: Pantothenate kinase catalyzes the rate-controlling step in coenzyme A (CoA) biosynthesis and is regulated by feedback inhibition CoA. was purified to homogeneity from Escherichia coli shown exist as a homodimer. Kinetic analysis indicated presence of two ATP binding sites that exhibited positive cooperativity with Hill coefficient 1.46. Site-directed mutagenesis lysine 101 methionine (K101M) resulted inactivation enzyme, although dimer formation not altered. The K101M mutant unable bind either adenosine 5'-O-(3-thiotriphosphate) or CoA, supporting conclusion kinetic both substrate inhibitor same site on enzyme. CoA cooperative. Coexpression gene high copy number plasmid chromosomal wild-type production heterodimers between active inactive subunits. chimeric showed absence cooperative interactions sequential mechanism for pantothenate first second. Thus, regulation involves competitive site, which blocks at one prevents second dimer.