Journal
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS
Volume 1851, Issue 3, Pages 248-260Publisher
ELSEVIER
DOI: 10.1016/j.bbalip.2014.12.012
Keywords
Channa striata; Delta 4 desaturase; Elongase; Long-chain polyunsaturated fatty acids biosynthesis; Nutritional regulation
Funding
- Universiti Sains Malaysia [RU 1001/PBIOLOGI/855003]
- EScience (Ministry of Agriculture and Agro-based Industry) [305/PBIOLOGI/613523]
- National Science Fellowship
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The endogenous production of long-chain polyunsaturated fatty acids (LC-PUFA) in carnivorous teleost species inhabiting freshwater environments is poorly understood. Although a predatory lifestyle could potentially supply sufficient LC-PUFA to satisfy the requirements of these species, the nutrient-poor characteristics of the freshwater food web could impede this advantage. In this study, we report the cloning and functional characterisation of an elongase enzyme in the LC-PUFA biosynthesis pathway from striped snakehead (Channa striata), which is a strict freshwater piscivore that shows high deposition of LC-PUFA in its flesh. We also functionally characterised a previously isolated fatty acyl desaturase cDNA from this species. Results showed that the striped snakehead desaturase is capable of Delta 4 and Delta 5 desaturation activities, while the elongase showed the characteristics of Elovl5 elongases. Collectively, these findings reveal that striped snakehead exhibits the genetic resources to synthesise docosahexaenoic acid (DHA; 22:6n-3) from eicosapentaenoic acid (EPA; 20:5n-3). Both genes are expressed at considerable levels in the brain and the liver. In liver, both genes were up-regulated by dietary C18 PUFA, although this increase did not correspond to a significant rise in the deposition of muscle LC-PUFA. Brain tissue of fish fed with plant oil diets showed higher expression of fads2 gene compared to fish fed with fish oil-based diet, which could ensure DHA levels remain constant under limited dietary DHA intake. This suggests the importance of DHA production from EPA via the Delta 4 desaturation step in order to maintain an optimal reserve of DHA in the neuronal tissues of carnivores. (C) 2015 Elsevier B.V. All rights reserved.
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