Synthesis of α2‐macroglobulin in rat hepatocyte and in a cell‐free system

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Abstract
The biosynthesis and secretion of α2‐macroglobulin was studied in rat hepatocytes primary cultures. After immunoprecipitation of α2‐macroglobulin from a cell homogenate and the hepatocyte medium, two forms of α2‐macroglobulin with app. M r of 176000 and 182000, respectively, were identified. A precursor—product relationship for the two α2‐macroglobulin forms was demonstrated by a pulse‐chase experiment. The cellular form of α2‐macroglobulin could be deglycosylated by endoglucosaminidase H, whereas the medium form of α2‐macroglobulin remained unaffected. On the other hand, only the medium form of α2‐macroglobulin was found to be susceptible to neuraminidase. In vitro translation of rat liver poly(A)+ RNA resulted in a translation product of an app. M r of 162000.