Two polycyclic aromatic hydrocarbon o-quinone reductases from a pyrene-degrading Mycobacterium.
Polycyclic aromatic hydrocarbon (PAH) o-quinone reductase (PQR) plays a crucial role in the detoxification of PAH o-quinones by reducing them to catechols. Two constitutive PQRs were found in cell extracts of a pyrene-degrading Mycobacterium sp. strain PYR100. The enzymes had an activity towards 9,10-phenanthrenequinone (PQ) and/or 4,5-pyrenequinone (PyQ), and the relative amounts varied with the pH of the culture media. PQR1, containing an FAD cofactor, was a monomer (20.1 kDa), and PQR2, with no flavin cofactor, was a homodimer (26.5 kDa subunits). There was no homology between the N-terminal sequences of PQR1 and PQR2. Dicumarol and quercetin inhibited PQR2 more strongly than PQR1. PQR1 had much lower specificity constants (k(cat)/K(m), 10(5)M(-1)s(-1)) for menadione (0.80) and PQ (5.19) than PQR2 (13.9 for menadione and 176 for PQ). Additionally, PQR2 exhibited a broad substrate specificity with high specificity constants for 1,4-naphthalenequinone, 1,2-naphthalenequinone, and PyQ.
Kim
Yong-Hak
YH
National Center for Toxicological Research, U.S. FDA, 3900 NCTR Rd., Jefferson, AR 72079-9502, USA.
Engesser
Karl-Heinrich
KH
Cerniglia
Carl E
CE
D000595:Amino Acid Sequence; D002457:Cell Extracts / Q000737:chemistry; D004789:Enzyme Activation; D005449:Fluorenes / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009161:Mycobacterium / Q000737:chemistry* / Q000145:classification / Q000201:enzymology / Q000378:metabolism*; D010616:Phenanthrenes / Q000378:metabolism; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism*; D011721:Pyrenes / Q000378:metabolism; D011808:Quinone Reductases / Q000096:biosynthesis / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D012988:Soil Microbiology; D013045:Species Specificity; D013379:Substrate Specificity
D002457:Cell Extracts; D005449:Fluorenes; D010616:Phenanthrenes; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; C007738:fluoranthene; C031181:phenanthrene; C030984:pyrene; D011808:Quinone Reductases