Direct Desaturation of Free Myristic Acid by Hen Liver Microsomal Δ9-Desaturase without Prior Activation to Myristoyl-CoA Derivative

Aziz C. Awad, Han Seung Shin, Dale R. Romsos, J. Ian Gray

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Direct desaturation of free myristic acid by hen liver microsomal Δ9-desaturase without prior activation to myristoyl-CoA by the addition of adenosine triphosphate (ATP) and CoA was observed when the incubation medium was mixed at mixing speeds of > 250 rpm in the presence of fatty acid-binding proteins (FABP). Desaturation was linear with time and proportional to the microsomal protein concentration. Desaturation was maximal at pH 7.9. The greatest desaturation rate was observed at a mixing speed of 500 rpm in the presence of FABP. Desaturation decreased at mixing speeds of >500 rpm. Data suggest that when myristic acid is bound to FABP in the form of protein-monomer complexes, its activation to the CoA derivative is not necessary for it to be desaturated by the Δ9-desaturase when using mixing rates of >250 rpm. Myristic acid-FABP complexes serve as substrates for the Δ9-desaturase at mixing rates of >250 rpm. Desaturation was reduced by bovine serum albumin and α -bromohexadecanoate, and no desaturation was observed in the absence of FABP. These findings suggest that FABP may regulate the accessibility of fatty acids in the desaturation reaction to the active site of the desaturase rather than just protect the membrane-bound desaturase from the cytotoxic effect of free fatty acids.

Original languageEnglish
Pages (from-to)3194-3201
Number of pages8
JournalJournal of Agricultural and Food Chemistry
Volume52
Issue number10
DOIs
StatePublished - 19 May 2004

Keywords

  • Deseturation
  • Enzymatic reaction
  • Fatty acid-binding protein
  • Free myristic acid
  • Myriatoleoyl-CoA

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