Catalyzes the dehydrogenation of glycerol 3-phosphate to dihydroxyacetone phosphate (PubMed:34555022). Is probably involved in anaerobic glycerol metabolism (Probable). Active in vitro with the artificial electron acceptor 2,6-dichlorophenolindophenol (DCPIP), but not with NAD or NADP. Also displays a very low oxidase activity in vitro on glycerol 3-phosphate with O2 as the electron acceptor, but this activity is most likely not physiological (PubMed:34555022). A + sn-glycerol 3-phosphate = AH2 + dihydroxyacetone phosphate Binds 1 [2Fe-2S] cluster. kcat is 0.24 sec(-1) with DCPIP as electron acceptor (at pH 7.4 and 25 degrees Celsius). Since this protein comes from the thermophilic bacterium C.mitchellensis, whose optimal growth temperature is 55 degrees Celsius, it can be speculated that its catalytic efficiency would be higher at higher experimental temperatures. Polyol metabolism; glycerol degradation via glycerol kinase pathway; glycerone phosphate from sn-glycerol 3-phosphate (aerobic route): step 1/1.