Kinetic isotope effect of the L-phenylalanine oxidase from Pseudomonas sp. P-501.
Pseudomonas L-phenylalanine oxidase (deaminating and decarboxylating) mainly catalyzes oxygenation when L-phenylalanine is used as the substrate, but oxidation when L-methionine is used as the substrate. Using [C(alpha)-H]-DL-methionine and [C(alpha)-D]-DL-methionine as substrate, the reductive half reaction of FAD cofactor of enzyme has been studied by stopped-flow spectrophotometry. The rate of reduction of FAD cofactor has a kinetic isotope effect (KIE) of 5.4 and 4.1 in the absence and presence of 30% glycerol, respectively. The KIE is independent of temperature, but the rates of the reductive half reaction are dependent on temperature, indicating that thermally induced motion at the active site drives the H-transfer reaction by H-tunneling.
Ohta
Yui
Y
Division of Biosciences, Graduate School of Fundamental Life Science, Kitasato University, Sagamihara, Kanagawa.
Mukouyama
Etsuko B
EB
Suzuki
Haruo
H
D000594:Amino Acid Oxidoreductases / Q000378:metabolism* / Q000502:physiology; D002384:Catalysis; D003903:Deuterium / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism; D007554:Isotopes; D007700:Kinetics; D008956:Models, Chemical; D011549:Pseudomonas / Q000201:enzymology*
D005420:Flavoproteins; D007554:Isotopes; D003903:Deuterium; D000594:Amino Acid Oxidoreductases; C022342:phenylalanine oxidase