Complementation analysis of human sialidase deficiency using natural substrates.

Complementation analysis by somatic cell hybridization to produce heterokaryons has shown that at least three complementation groups exist within the disorders in which the enzyme sialidase is deficient. We have confirmed these results by electrophoretic analysis of two glycoprotein enzymes, adenosine deaminase and acid phosphatase, which show aberrant electrophoretic mobilities in these disorders. These abnormal forms, which have excess sialic acid bound, disappear on complementation and are replaced by normal mobility components. It is suggested that the sialidase produced on complementation uses the abnormal forms as natural substrates and that they may represent normal intermediates in the processing of glycoprotein enzymes.