Molecular cloning and sequence analysis of stearoyl-CoA desaturase in milkfish, Chanos chanos

Stearoyl-CoA desaturase (EC 1.14.99.5) is a key enzyme in the biosynthesis of polyunsaturated fatty acids and the maintenance of the homeoviscous flui dity of biological membranes. The stearoyl-CoA desaturase cDNA in milkfish Chanos chanos) was cloned by RT-PCR and RACE, and it was compared with the stearoyl-CoA desaturase in cold-tolerant teleosts, common carp and grass ca rp. Nucleotide sequence analysis revealed that the cDNA clone has a 972-bp open reading frame encoding 323 amino acid residues. Alignments of the dedu ced amino acid sequence showed that the milkfish stearoyl-CoA desaturase sh ares 79% and 75% identity with common carp and grass carp, and 63%-64% with other vertebrates such as sheep, hamsters, rats, mice, and humans. Like co mmon carp and grass carp, the deduced amino acid sequence in milkfish well conserves three histidine cluster motifs (one HXXXXH and two HXXHH) that ar e essential for catalysis of stearoyl-CoA desaturase activity. However, RT- PCR analysis showed that stearoyl-CoA desaturase expression in milkfish is detected in the tissues of liver, muscle, kidney, brain, and gill, and more expression sites were found in milkfish than in common carp and grass carp . Phylogenic relationships among the deduced stearoyl-CoA desaturase amino acid sequence in milkfish and those in other vertebrates showed that the mi lkfish stearoyl-CoA desaturase amino acid sequence is phylogenetically clos er to those of common carp and grass carp than to other higher vertebrates. (C) 2001 Elsevier Science Inc. All rights reserved.