[Isoform 1]: Electrogenic Na+-coupled sugar symporter that actively transports D-mannose or D-fructose at the plasma membrane, with a Na+ to sugar coupling ratio of 1:1. Transporter activity is driven by a transmembrane Na+ electrochemical gradient set by the Na+/K+ pump. Exclusively recognizes sugar substrates having a pyranose ring with an axial hydroxyl group on carbon 2 (PubMed:22212718, PubMed:23451068, PubMed:24573086). Has likely evolved to enable renal reabsorption of D-mannose, an important constituent of oligosaccharide chains of glycoproteins. Contributes to dietary D-fructose reabsorption from glomerular filtrate across the brush border of the kidney (PubMed:22212718, PubMed:23451068). {ECO:0000269|PubMed:22212718, ECO:0000269|PubMed:23451068, ECO:0000269|PubMed:24573086}. [Isoform 2]: Appears to have no transporter activity. . This is the function of SLC5A10 (solute carrier family 5 member 10, ENSG00000154025).