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Electrophoretic characterization of posttranslational modifications of human parotid salivary α‐amylase
Author(s) -
Bank Ruud A.,
Hettema Ewald H.,
Arwert Fré,
Amerongen Arie V. Nieuw,
Pronk Jan C.
Publication year - 1991
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150120114
Subject(s) - deamidation , chemistry , biochemistry , glycosylation , oligosaccharide , isozyme , sialic acid , amylase , band 3 , glycan , polyacrylamide gel electrophoresis , enzyme , glycoprotein , membrane protein , membrane
Human salivary α‐amylase displays multiple bands upon native polyacrylamide gel electrophoresis. In fresh saliva, due to posttranslational modifications, a pattern of 5–6 isozymes is observed. The isozymes are designated 1–6, in the order of increasing anodal mobilty. As a result of the development of a rapid and sensitive electrophoresis system, with markedly higher resolution than previously reported, we concluded that a previously proposed model (Karn et al., Biochem. Genet . 1973, 10 , 341–350) is inadequate to explain the origin of the various bands. We propose an alternative model that fits in with our new and previously made observations. According to this model, band 2 is the primary gene product and band 1 is its glycosylated counterpart with only one neutral oligosaccharide present on each molecule. Band 3 originates from band 1 by the transialidase‐catalyzed incorporation of sialic acid into the biantennary chain. Bands 4 and 6 originate from bands 2 and 4, respectively, by deamidation; band 5 is the deamidation product of amylase with an acidic oligosaccharide (band 3). Only a minor part of band 3 consists of the deamidation product of band 1. Peptide Asn‐Gly‐Ser (residues 427–429) is the most probable candidate for glycosylation; literature data suggests that deamidation occurs in the stretch Glu‐Asn‐Gly‐Lys‐Asp (residues 364–368) and Asn‐Gly‐Asn‐Cys (residues 474–477). Both glycosylation and deamidation might play a role in the clearance of amylase from the systemic circulation. The elecroporesis system described is a powerful tool to determine amylase isozyme distributions in health and disease, especially for the screening of alterations seen in ectopically produced amylase.