These catalytically active enzymes are derived from rat liver and affinity purified. The Yb1(GS22) is a 26.5 kDa enzyme and homodimer with an isoelectric point of 8.5. The Yb2 (GS24) is a again a 26.5 kDa homodimer but with a 7.0 isoelectric point. These are useful for enzyme assays or as standards in Western blots.