title: A systematic and comprehensive combinatorial approach to simultaneously improve the activity, reaction specificity, and thermal stability of p-hydroxybenzoate hydroxylase.
abstract: We have simultaneously improved the activity, reaction specificity, and thermal stability of p-hydroxybenzoate hydroxylase by means of systematic and comprehensive combinatorial mutagenesis starting from available single mutations. Introduction of random mutations at the positions of four cysteine and eight methionine residues provided 216 single mutants as stably expressed forms in Escherichia coli host cells. Four characteristics, hydroxylase activity toward p-hydroxybenzoate (main activity), protocatechuate-dependent NADPH oxidase activity (sub-activity), ratio of sub-activity to main activity (reaction specificity), and thermal stability, of the purified mutants were determined. To improve the above characteristics for diagnostic use of the enzyme, 11 single mutations (C152V, C211I, C332A, M52V, M52Q, M110L, M110I, M213G, M213L, M276Q, and M349A) were selected for further combinatorial mutagenesis. All possible combinations of the mutations provided 18 variants with double mutations and further combinatorial mutagenesis provided 6 variants with triple mutations and 9 variants with quadruple mutations with the simultaneously improved four properties.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Suemori
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iwakura
mesh_terms: D015109:4-Hydroxybenzoate-3-Monooxygenase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004795:Enzyme Stability / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006358:Hot Temperature; D016296:Mutagenesis; D020125:Mutation, Missense; D019255:NADPH Oxidases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D010226:Parabens / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D010226:Parabens; D011994:Recombinant Proteins; D015109:4-Hydroxybenzoate-3-Monooxygenase; D019255:NADPH Oxidases; C038193:4-hydroxybenzoic acid