title: Fatty aldehyde dehydrogenases in Acinetobacter sp. strain HO1-N: role in hexadecanol metabolism.
abstract: The role of fatty aldehyde dehydrogenases (FALDHs) in hexadecane and hexadecanol metabolism was studied in Acinetobacter sp. strain HO1-N. Two distinct FALDHs were demonstrated in Acinetobacter sp. strain HO1-N: a membrane-bound, NADP-dependent FALDH activity induced 5-, 15-, and 9-fold by growth on hexadecanol, dodecyl aldehyde, and hexadecane, respectively, and a constitutive, NAD-dependent, membrane-localized FALDH. The NADP-dependent FALDH exhibited apparent Km and Vmax values for decyl aldehyde of 5.0, 13.0, 18.0, and 18.3 microM and 537.0, 500.0, 25.0, and 38.0 nmol/min in hexadecane-, hexadecanol-, ethanol-, palmitate-grown cells, respectively. FALDH isozymes ald-a, ald-b, and ald-c were demonstrated by gel electrophoresis in extracts of hexadecane- and hexadecanol-grown cells. ald-a, ald-b, and ald-d were present in dodecyl aldehyde-grown cells, while palmitate-grown control cells contained ald-b and ald-d. Dodecyl aldehyde-negative mutants were isolated and grouped into two phenotypic classes based on growth: class 1 mutants were hexadecane and hexadecanol negative and class 2 mutants were hexadecane and hexadecanol positive. Specific activity of NADP-dependent FALDH in Ald21 (class 1 mutant) was 85% lower than that of wild-type FALDH, while the specific activity of Ald24 (class 2 mutant) was 55% greater than that of wild-type FALDH. Ald21R, a dodecyl aldehyde-positive revertant able to grow on hexadecane, hexadecanol, and dodecyl aldehyde, exhibited a 100% increase in the specific activity of the NADP-dependent FALDH. The oxidation of [3H]hexadecane byAld21 yielded the accumulation of 61% more fatty aldehyde than the wild type, while Ald24 accumulated 27% more fatty aldehyde, 95% more fatty alcohol, and 65% more wax ester than the wild type. This study provides genetic and physiological evidence for the role of fatty aldehyde as an essential metabolic intermediate and NADP-dependent FALDH as a key enzyme in the dissimilation of hexadecane, hexadecanol, and dodecyl aldehyde in Acinetobactor sp. strain HO1-N.
mesh_terms: D000150:Acinetobacter / Q000201:enzymology*; D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism; D000473:Alkanes / Q000378:metabolism*; D004790:Enzyme Induction; D005227:Fatty Acids / Q000378:metabolism; D005233:Fatty Alcohols / Q000378:metabolism*; D007700:Kinetics; D008566:Membranes / Q000201:enzymology; D009154:Mutation; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D013696:Temperature
chemical_list: D000447:Aldehydes; D000473:Alkanes; D005227:Fatty Acids; D005233:Fatty Alcohols; D009243:NAD; D009249:NADP; C005031:cetyl alcohol; D000444:Aldehyde Dehydrogenase; C007932:n-hexadecane