[Substrate specificity of three murine GDP-fucose: beta-galactoside alpha1,2-fucosyltransferases]

OBJECTIVE

To compare the substrate specificity of three murine GDP fucose: beta-galactoside alpha1,2-fucosyltransferases (alpha1,2-FT).

METHODS

Three members of MFUT- I, -II and -III, coding for a alpha1,2-FT, a GDP-fucose, were cloned from a cDNA of murine small intestine by reverse transcription-polymerase chain reaction. The coding regions were ligated into mammalian expression vector pcDNA 3.1 (pcDNA3.1-MFUT-I, pcDNA3.1-MFUT- II , and pcDNA3.1-MFUT- III) and were transiently transfected into COS-7 cells using a cellphect transfection kit. Then the cells were analyzed for expression and function of alpha1,2-FT and the substrate specificity of three alpha1,2-FT was compared.

RESULTS

MFUT- I, -II, and -III exhibited sequence homology with human H (77%), Se (79%), and Sec1 (75%) genes, respectively. COS-7 cells transfected with pcDNA3.1-MFUT- I and pcDNA3.1-MFUT- II showed alpha1,2-FT activity, but no activity was detected in COS-7 cells transfected with pcDNA3.1- MFUT-III. MFUT- II showed alpha1,2-FT activity with both asialo-monosialoteterahexosyl ganglioside (GA1) and monosialoteterahexosyl ganglioside (GM1) as substrates to produce fucosyl GA1(FGA1) and fucosyl GM1(FGM1), respectively, but MFUT- I only showed alpha1,2-FT activity with GA1. The relative activity of MFUT- II with GA1 was 80-90-folds higher compared with MFUT- I, and the relative activity of MFUT- II with GA1 was 10-20-folds higher than that of GM1. The fucosyltransferase encoded by the MFUT- II gene showed the enzyme activity not only responsible for the synthesis of type 4-H antigens FGA1 and FGM1, but also responsible for the synthesis of type 1-H and 2-H antigens with lactotetraosylceramide and neolactotetraosylceramide as substrates.

CONCLUSION

MFUT- II is the main alpha1,2-FT in mouse and MFUT- II can product type 4-H antigen FGA1 and FGM1, but MFUT- I only synthesizes FGA1. MFUT-III has no alpha1,2-FT activity.