Abstract
A recently identified Δ6 fatty acid desaturase in Mucor rouxii shows a low sequence homology (~24% at the amino acid level) to that isolated from Mortierella alpina, but is phylogenetically closer to a plant enzyme, suggesting the occurrence of Δ6 desaturase isozymes in Mucorales molds. In the present study, two types of Δ6 desaturases, mcD6-1 (Mo. alpina type) and mcD6-2 (M. rouxii type), were cloned from Mucor circinelloides. When the cloned genes were expressed in the yeast Saccharomyces cerevisiae in the presence of a linoleic acid substrate (C18:2Δ9, 12), a newly generated γ-linolenic acid (C18:3Δ6, 9, 12) was detected in the cells, which confirmed the suspected enzymatic function of the recombinant protein. This is the first report of Δ6 desaturase isozymes present in one organism. Northern analysis demonstrated that the amount of mcD6-2 mRNA was less than half of that of mcD6-1 mRNA in cells grown at 28 °C. However, upon cultivation of the cells at 15 °C for 0.5–1 h, mcD6-2 mRNA rapidly increased by up to 1.5-fold and then gradually decreased. By contrast, mcD6-1 transcripts levels did not fluctuate significantly for 1 h after the temperature shift, but declined by 75% over the next 2 h. The γ-linolenic acid content in total fatty acid from M. circinelloides decreased at 28 °C, but was maintained at approximately 30% at 15 °C. These data suggest that Δ6 desaturase isozymes play physiologically distinct roles in the maintenance of cellular lipids and adaptation to low temperature.
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Michinaka, Y., Aki, T., Shimauchi, T. et al. Differential response to low temperature of two Δ6 fatty acid desaturases from Mucor circinelloides . Appl Microbiol Biotechnol 62, 362–368 (2003). https://doi.org/10.1007/s00253-003-1326-3
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DOI: https://doi.org/10.1007/s00253-003-1326-3