Cloning Of CDNA And RT-PCR Expression Analysis Of BHMT In Lateolabrax Japonicus

Betaine homocysteine methyltransferase(BHMT, EC 2.1.1.5) catalyzes the transfer of methyl group from betaine to homocysteines(Hcy) to form dimethylglycine and Met, respectively.A full-length cDNA of the BHMT (betaine homocysteine methyltransferase) in Lateolabrax japonicus was amplified by RT-PCR and SMART RACE method. The cDNA of the BHMT in Lateolabrax japonicus is 1461bp in size, with 1151bp 5'-UTR, 517bp 3'-UTR and 1206bp ORF, encoding a protein of 401 amino acids with a molecular weight of 44.32kDa and pI 7.21. The sequence analysis indicated that the deduced amino acid sequence of the cDNA shared high identity with other ten species, such as Perca flavescens, Sparus aurata, Salmo salar, Danio rerio, Paralichthys olivaceus, Xenopus laevis, Homo sapiens, Pan troglodytes, Mus musculus and Bos taurus, which is from 77% to 93%, and the highest is 93% with Perca flavescens. This enzyme contain the following motif: G[ILV]NCX(20,100) and [ALV]X(2)[ILV]GGCCX(3)PX(2)I.Semi-quantitative RT-PCR was used to characterize the expression of BHMT in ten tissues, ten tissues including muscle, heart, eye, brain, gill, liver, intestine, kidney, adipose tissue and spleen. The results showed that BHMT is only expressed in liver, intestine and kidney. BHMT mRNA in these three tissues were reduced after the fish was transferred to higher salinity of 29 from sea water of salinity 25 and were induced after transferred to lower salinity of 12. BHMT gene in liver, intestine and kidney can be induced too after intraperitoneal injection of betaine. The results showed betaine can induce the transcription of BHMT in fish, and BHMT play pivotal roles in adaptation to osmotic changes ambience.