Biotinidase and lipoamidase in guinea pig livers

Guinea pig biotinidase and lipoamidase were mostly located in the liver microsomal fraction. Approx. 80% of the total activities of both enzymes were associated with the membranes subfractions of liver. The subunit molecular masses of these enzymes as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of microsomal biotinidase and lipoamidase were 70 and 60 kDa, respectively. Sephadex G-200 gel-permeation chromatography in the presence of 0.1% Nonidet P-40 indicated that the native-state molecular masses of microsomal biotinidase and lipoamidase were 68 and 120 kDa, respectively. The isoelectric points of microsomal biotinidase and lipoamidase were 6.3 and 5.7, respectively. Linear sucrose density centrifugation analysis indicated that both enzymes exist in the rough endoplasmic reticulum. Comparison of amino acid analyses indicated a higher content of leucine and lower content of serine in lipoamidase than in biotinidase. Microsomal biotinidase and lipoamidase were classified as being thiol-type and serine-type amidases, respectively.