Conversion of glycerol 3-phosphate to dihydroxyacetone. Uses fumarate or nitrate as electron acceptor. a quinone + sn-glycerol 3-phosphate = a quinol + dihydroxyacetone phosphate Polyol metabolism; glycerol degradation via glycerol kinase pathway; glycerone phosphate from sn-glycerol 3-phosphate (anaerobic route): step 1/1. Composed of a catalytic GlpA/B dimer and of membrane bound GlpC. Belongs to the anaerobic G-3-P dehydrogenase subunit B family.