Poly(vinyl alcohol) dehydrogenase (PVADH-S) purified from Pseudomonas sp, 113P3 dehydrogenized poly(vinyl alcohol) (PVA), but the enzyme reaction was significantly affected by changing the properties of PVA, in terms of saponification degree, ethylene content, polymerization degree, tacticity, and 1,2-glycol content. The apparent V-max/K-m value of PVA containing 10 mol% ethylene was over 10-fold greater than that of PVA. The hydrophobicity of PVA-related polymers might be important in the affinity for the PVADH-S.