Freshly isolated rat hepatocytes were found to contain a 3-fold higher level of putrescine than perfused liver. The bulk of this diamine was recovered in the acid-insoluble fraction of the cell. In order to determine the nature of the amine binding, the levels of γ-glutamylamine derivatives were measured. The method used involves exhaustive proteolytic digestion of the acid-insoluble fraction of hepatocytes, followed by ion-exchange chromatography. For N1-(γ-glutamyl)putrescine, a combined ion-exchange chromatographic and reverse-phase h.p.l.c procedure was adopted. This allowed for the direct detection of less than 50 pmol of this derivative in enzymic hydrolysates. Several of the γ-glutamylamines reported previously [Beninati, Piacentini, Argento-Ceru', Russo-Caia & Autuori (1985) Biochim. Biophys. Acta 841, 120-126] in the whole organ were found in the isolated liver cells. The elevated level of N1-(γ-glutamyl)putrescine and the absence of bis-(γ-glutamyl)spermine was noteworthy. The results suggest that, in rat hepatocytes, both polyamine-dependent post-translational modification of some proteins and cross-linking between proteins involving the glutamine and lysine residues occurs.
|Number of pages||5|
|Publication status||Published - 1988|
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