Storage protein of tuber. Involved in protection against oxidative stress (Probable). Has carbonate dehydratase, trypsin inhibitor, dehydroascorbate (DHA) reductase and monodehydroascorbate (MDA) reductase activities (PubMed:22195572). Catalyzes the reactions of carbonate dehydratase and DHA reductase independently of zinc and glutathione (GSH). The coupled reaction is capable of recycling a plant antioxidant ascorbate using ubiquitous compounds H(2)O and CO(2) (PubMed:25747844). Exhibits antioxidant activity. Able to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Exhibits immunomodulatory activity. Activates Toll-like receptor 4 signaling pathways by up-regulating the gene expression of pro-inflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 beta and interleukin-6, and chemokines RANTES and MCP-1, in mouse RAW 264.7 macrophages. Stimulates the phagocytosis of E.coli by the LPS-treated mouse macrophages (PubMed:22796748). H(+) + hydrogencarbonate = CO2 + H2O H(+) + 2 monodehydro-L-ascorbate radical + NADH = 2 L-ascorbate + NAD(+) The carbonate dehydratase activity is not substantially changed by the addition of Zn(2+). kcat is 0.0152 min(-1) for DHA. kcat is 30500 min(-1) for sodium bicarbonate. Monomer (PubMed:22806688). Homodimer (By similarity). Expressed in tuber (at protein level). Not glycosylated. Causes an allergic reaction in human (Probable). Belongs to the alpha-carbonic anhydrase family. Despite overall sequence similarity to the typical alpha class carbonic anhydrases, lacks one of the three conserved catalytic zinc-ligand histidines. The carbonate dehydratase activity of this protein is zinc-independent.