Functional lysosomal hydrolase size as determined by radiation inactivation analysis

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Abstract
Electron inactivation analysis with 16 MeV electrons was used to determine the functional target size of a number of commonly studied lysosomal hydrolases. Observed values ranged from a low of 62,000 .+-. 4000 Da [daltons] for .beta.-galactosidase to a high of 200,000 .+-. 17,500 Da (mouse .beta.-glucuronidase). One group of lysosomal hydrolases (N-acetyl-.beta.-glucosaminidase, N-acetyl-.beta.-galactosaminidase, .alpha.-galactosidase, .beta.-mannosidase, .beta.-glucosidase, arylsulfatase A and sphingomyelinase) had target sizes in the range 100,000-120,000 Da; .alpha.-glucosidase and .alpha.-fucosidase exist as complex multimers in the 150,000-160,000 Da range. Analysis of freeze-dried cell material showed little evidence of species (mouse vs. human) variation in the functional size of most lysosomal hydrolases with the exception of .beta.-glucuronidase. The potential usefulness of lysosomal hydrolases as endogenous marker enzymes in studies where the target size of proteins of unknown molecularmass is to be determined is suggested.