Catalyzes the hydration of acetylene to form acetaldehyde. Ethylene cannot act as a substrate. acetaldehyde = acetylene + H2O Binds 1 [4Fe-4S] cluster. Binds 1 W-bis(molybdopterin guanine dinucleotide) (W-bis-MGD) cofactor per subunit. Optimum pH is 6.0-6.5. Optimum temperature is 50 degrees Celsius. Monomer. The tungsten center binds a water molecule that is activated by Asp-13 residue, enabling it to attack acetylene bound in a distinct hydrophobic pocket. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.