Hydrolases of pulmonary lysosomes and lamellar bodies.

Lamellar bodies and lysosomes from the lungs of rabbits were examined for the presence of 24 hydrolytic enzymes. All hydrolases detectable in lysosomes were also found in lamellar bodies. Hydrolase activities in lamellar bodies were not due to contamination with lysosomes as shown by isopycnic centrifugation of the subcellular organelles on continuous density sucrose gradients. Lysosomal preparations were also free of lamellar bodies. In lysosomes the acid hydrolases with the highest specific activities were P-N-acetylglucosaminidase > acid phosphatase > acid pyrophosphatase > a-mannosidase, and in lamellar bodies the most active were 8-N-acetylglucosaminidase > a-mannosidase = acid phosphatase > acid pyrophosphatase. Acid phospholipase A activities were present in lamellar bodies as well as in lysosomes. The presence of hydrolases in lamellar bodies was not due to adsorption of enzyme to the structures during their isolation. Multiple forms of several hydrolases were compared using polyacrylamide gel electrophoresis. Both A and B forms of P-N-acetylglucosaminidase were present in lamellar bodies and lysosomes; however, the ratio of these two forms differed, being A:B = 35:l in lysosomes and A:B = 16:l in lamellar bodies. Single forms of a-Nacetylglucosaminidase and a-mannosidase were present in both organelles. Three forms of acid phosphatase were present, but the ratios between the forms differed between the two organelles. Hydrolases were released less readily from lamellar bodies than from lysosomes by disruptive agents and processes such as detergents and sonication. These studies indicate that lysosomaltype hydrolases are normal components of lamellar bodies and that their hydrolase complement is remarkably similar to that of lysosomes.