Biosynthesis of Polyunsaturated Fatty Acids in Octopus vulgaris: Molecular Cloning and Functional Characterisation of a Stearoyl-CoA Desaturase and an Elongation of Very Long-Chain Fatty Acid 4 Protein.

Óscar Monroig,Sergi Puig,Rosa De Llanos,Inmaculada Varó,Juan Navarro,Douglas Tocher,Francisco Hontoria

doi:10.3390/md15030082

Abstract

Polyunsaturated fatty acids (PUFAs) have been acknowledged as essential nutrients for cephalopods but the specific PUFAs that satisfy the physiological requirements are unknown. To expand our previous investigations on characterisation of desaturases and elongases involved in the biosynthesis of PUFAs and hence determine the dietary PUFA requirements in cephalopods, this study aimed to investigate the roles that a stearoyl-CoA desaturase (Scd) and an elongation of very long-chain fatty acid 4 (Elovl4) protein play in the biosynthesis of essential fatty acids (FAs). Our results confirmed the Octopus vulgaris Scd is a ∆9 desaturase with relatively high affinity towards saturated FAs with ≥ C18 chain lengths. Scd was unable to desaturate 20:1n-15 (∆520:1) suggesting that its role in the biosynthesis of non-methylene interrupted FAs (NMI FAs) is limited to the introduction of the first unsaturation at ∆9 position. Interestingly, the previously characterised ∆5 fatty acyl desaturase was indeed able to convert 20:1n-9 (∆1120:1) to ∆5,1120:2, an NMI FA previously detected in octopus nephridium. Additionally, Elovl4 was able to mediate the production of 24:5n-3 and thus can contribute to docosahexaenoic acid (DHA) biosynthesis through the Sprecher pathway. Moreover, the octopus Elovl4 was confirmed to play a key role in the biosynthesis of very long-chain (>C24) PUFAs.

Highlights

Cephalopods have been regarded as promising candidates for the diversification of marine aquaculture due to their great commercial interest [1]
Our results showed that the O. vulgaris stearoyl-CoA desaturase (Scd) was unable to desaturate the substrate 20:1 (20:1n‐15) to ∆5,920:2 (Figure 5a), yeast transformed with pYES2‐fatty acyl desaturase (Fad) were able to
This partly explains the considerable interest in elucidating the polyunsaturated fatty acids (PUFAs) biosynthetic pathways in aquatic and marine species, in farmed fish for which current trends in feed formulation are impacting the nutritional quality for human consumers [32]

Summary

Introduction

Cephalopods have been regarded as promising candidates for the diversification of marine aquaculture due to their great commercial interest [1]. Despite significant progress made over the last decade, culture of cephalopod species with pelagic paralarval stages like the common octopus. The specific factors causing such mortalities of paralarvae remain unclear, it has become increasingly obvious that nutritional issues associated with inadequate supply of essential. Mar. Drugs 2017, 15, 82; doi:10.3390/md15030082 www.mdpi.com/journal/marinedrugs. Mar. Drugs 2017, 15, 82 nutrients such as lipids are crucial to ensure normal growth and development of O. vulgaris paralarvae and improve their viability [3]. Previous investigations postulated that polyunsaturated fatty acids (PUFAs) are essential nutrients for the common octopus [4,5]. The specific PUFAs that satisfy the physiological requirements were not determined, partly due to the difficulties in running nutritional trials on octopus paralarvae

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Conclusion