title: Catabolism of L-phenylalanine and L-tyrosine by Rhodobacter sphaeroides OU5 occurs through 3,4-dihydroxyphenylalanine.
abstract: Rhodobacter sphaeroides OU5 utilized l-phenylalanine as sole source of nitrogen for growth. The metabolites of l-phenylalanine catabolism, i.e. 4-hydroxy phenylalanine (l-tyrosine), 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenyl-pyruvic acid (DOPP), 3,4-dihydroxyphenyllactic acid (DOPLA), 3,4-dihydroxyphenyl-acetic acid (DOPAc) and 3,4-dihydroxybenzoic acid (PC), were identified using liquid chromatography-mass spectroscopy (LC-MS). With 2-oxoglutarate as an amino acceptor, DOPA aminotransferase activity was observed with cell-free extracts and the product DOPP was confirmed through mass analysis. Reductive deamination of DOPA also occurred in the absence of 2-oxoglutarate, whose products were 3,4-dihydroxyphenylpropionic acid (DPPA) and ammonia. The enzyme DOPA-reductive deaminase (DOPARDA) was purified to its homogeneity and characterized. DOPARDA has an obligate requirement for NADH and is functional at low concentrations of the substrate (<150 microM). The molecular mass of the purified enzyme was approximately 274kD and the enzyme could be a heterotetramer of 110, 82, 43 and 39kD subunits as determined by SDS-PAGE.
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, P.O. Central University, Hyderabad 500 046, India.
authors.forename: N K
authors.initials: NK
authors.lastname: Ranjith
authors.forename: Ch
authors.initials: Ch
authors.lastname: Sasikala
authors.forename: Ch V
authors.initials: ChV
authors.lastname: Ramana
mesh_terms: D002474:Cell-Free System; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D014443:Tyrosine; D010649:Phenylalanine; D004295:Dihydroxyphenylalanine