Open AccessA membrane‐associated protein with Cr(VI)‐reducing activity from Thermus scotoductus SA‐01
Author(s) -
Opperman Diederik Johannes,
Van Heerden Esta
Publication year - 2008
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2007.01063.x
Subject(s) - dihydrolipoamide dehydrogenase , thermus thermophilus , flavin group , flavin adenine dinucleotide , reductase , nad+ kinase , cofactor , chemistry , biochemistry , enzyme , oxidoreductase , active site , dehydrogenase , gene , escherichia coli
A membrane‐associated chromate reductase from Thermus scotoductus SA‐01 has been purified to apparent homogeneity and shown to couple the reduction of Cr(VI) to NAD(P)H oxidation, with a preference towards NADH. The chromate reductase is a homodimer with a monomeric molecular weight of 48 kDa and a noncovalently bound FAD coenzyme. The enzyme is optimally active at a pH of 6.5 and 65 °C with a K m of 55.5±4.2 μM and a V max of 2.3±0.1 μmol Cr(VI) min −1 mg −1 protein. The catalytic efficiency ( k cat / K m ) of the enzyme was found to be comparable to that found for quinone reductases but more efficient than the nitroreductases. N‐terminal sequencing and subsequent screening of a genomic library of T. scotoductus revealed an ORF of 1386 bp, homologous (84%) to the dihydrolipoamide dehydrogenase gene of Thermus thermophilus HB8. These results extend the knowledge of chromate reductases mediating Cr(VI) reduction via noncovalently bound or free redox‐active flavin groups and the activity of dihydrolipoamide dehydrogenases towards physiologically unrelated substrates.