Mycolic acid synthesis by Mycobacterium aurum cell-free extracts.
The first cell-free system capable of synthesizing whole mycolic acids: (R1CH(OH)CH(R2)COOH, with 60 to 90 carbon atoms) from [1-14C]acetate is described and preliminary investigations into some of its requirements and properties are reported. Biosynthetic activity for mycolic acids occurred in an insoluble fraction (40 000 X g pellet) from disrupted cells of Mycobacterium aurum (ATCC 23366-type strain); it produced mycolic acids, but a very small amount of non-hydroxylated fatty acids. The predominant product was unsaturated mycolic acid (type I), while oxo- (type IV) and dicarboxy- (type VI) mycolic acids were synthesized to a lesser extent. When [1-14C]palmitic acid was used as a marker, no labelled mycolic acid was detected. The reaction required a divalent cation (Mg2+ or Mn2+), KHCO3 and O2. Neither CoA, NADH, NADPH nor ATP were necessary, but CoA rather increased the synthesis of non-hydroxylated fatty acids. Glucose or trehalose were not required. Avidin inhibited the biosynthesis of the three types of mycolic acid indicating the presence of a biotin-requiring enzyme in the reaction sequence and therefore a carboxylation step, but citrate had no allosteric effect. Iodoacetamide inhibited the system. These first data are in favor of a complex multienzyme system.
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Centre de Recherches de Biochimie et Génétique Cellulaires, Université Paul Sabatier, Toulouse, France.
Lanéelle
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D000085:Acetates / Q000378:metabolism; D002021:Buffers; D002474:Cell-Free System; D055598:Chemical Phenomena; D002621:Chemistry; D009161:Mycobacterium / Q000378:metabolism* / Q000648:ultrastructure; D009171:Mycolic Acids / Q000302:isolation & purification*; D013997:Time Factors
D000085:Acetates; D002021:Buffers; D009171:Mycolic Acids