Fatty acid activation by a lipophilic bacterium

Area of Science:

• Microbiology
• Biochemistry
• Enzymology

Background:

• Nocardia asteroides is an actinomycete bacterium known for its metabolic capabilities.
• Fatty acid activation is a crucial initial step in various metabolic pathways, including beta-oxidation and lipid synthesis.
• Acyl-coenzyme A (CoA) synthetases (ACS) are enzymes responsible for catalyzing this activation process.

Purpose of the Study:

• To investigate the fatty acid activation capabilities of Nocardia asteroides.
• To characterize the enzyme responsible for fatty acid activation in N. asteroides.
• To determine the substrate specificity and cofactor requirements of the identified enzyme.

Main Methods:

• Preparation of cell-free extracts from Nocardia asteroides.
• Assay of fatty acid activation using various chain lengths of fatty acids.
• Enzyme characterization, including determination of cofactor requirements and kinetic analysis.
• Enzyme localization studies within the bacterial cell.

Main Results:

• Cell-free extracts of N. asteroides activated saturated fatty acids ranging from octanoate (C8) to octadecanoate (C18), with maximal activation observed for dodecanoate (C12).
• No activation was observed for short-chain fatty acids.
• The activating enzyme was identified as an acyl-coenzyme A (CoA) synthetase (EC 6.2.1.3), localized in the cytoplasm.
• The enzyme exhibited absolute requirements for coenzyme A, adenosine 5'-triphosphate (ATP), and Mg(2+).
• Kinetic data indicated the presence of at least two distinct synthetases: one for short-chain fatty acids and another for medium- and long-chain fatty acids.

Conclusions:

• Nocardia asteroides possesses a cytoplasmic acyl-CoA synthetase system capable of activating medium- and long-chain fatty acids.
• The enzyme system demonstrates specificity for fatty acid chain length, suggesting the existence of multiple synthetases.
• Understanding these enzymes provides insight into the lipid metabolism of Nocardia asteroides.