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