a lactoside IV(2),III(4)-a-[Fuc]2-Lc4Cer + GDP + H(+) => a lactoside III(4)-a-Fuc-Lc4Cer + GDP-beta-L-fucose
a lactoside iv(2),iii(4)-a-[fuc]2-lc4cer + gdp + h(+) => a lactoside iii(4)-a-fuc-lc4cer + gdp-beta-l-fucose