Storage protein of tuber. Involved in protection against oxidative stress (Probable). Has carbonate dehydratase and weak trypsin inhibitor activity detected by measuring the dehydration of sodium bicarbonate and the inhibition of trypsin-catalyzed hydrolysis of N-benzoyl-L-arginine-4-nitro anilide, respectively (PubMed:10552514). Contrarily, no carbonate dehydratase or trypsin inhibitor activity detected by measuring the hydrolysis of 4-nitrophenyl acetate or the inhibition of bovine trypsin-catalyzed hydrolysis of N-benzoyl-L-arginine ethyl ester, respectively (PubMed:15047697). Has dehydroascorbate (DHA) reductase and monodehydroascorbate (MDA) reductase activities (Ref.5). 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) (By similarity). Exhibits antioxidant activity. Able to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radicals (PubMed:11600050). 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 (By similarity). H(+) + hydrogencarbonate = CO2 + H2O H(+) + 2 monodehydro-L-ascorbate radical + NADH = 2 L-ascorbate + NAD(+) Monomer (By similarity). Homodimer (PubMed:15047697). Expressed in tuber (at protein level). Not glycosylated. Causes an allergic reaction in human. Binds to IgE of patients allergic to Chinese yam (PubMed:18303202, PubMed:29423371). Patients can be sensitized to this protein via an oral or inhalant route (PubMed:18303202). Thermal stable oral allergen, which can to trigger anaphylactic reaction and oral allergy syndrome even when consumed as cooked. Activates human basophils (PubMed:29423371). Belongs to the alpha-class 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. It is uncertain whether the mature protein starts at position 22 or 23. The first residue of the N-terminus obtained by direct protein sequencing is 'Asn-22' according to PubMed:18303202, but it is 'Val-23' according to PubMed:15047697, PubMed:10552514 and PubMed:29423371.