an inositol-1-phosphodihydroceramide + GDP-alpha-D-mannose => an alpha-D-mannosylinositol-1-phosphodihydroceramide + GDP + H(+)
an inositol-1-phosphodihydroceramide + gdp-alpha-d-mannose => an alpha-d-mannosylinositol-1-phosphodihydroceramide + gdp + h(+)