Electrophoretic mobility of external invertase from free and gel-immobilized yeast cells

Electrophoretic mobility of secreted invertase (E.C.3.2.1.26) from gelatin immobilized yeast cells was analyzed and prepared with that of secreted invertase from freely suspended batch grown cells. Invertase from immobilized cells showed a lower mobility after 24 h opf incubation, in medium containing either glucose or raffinose as carbon source. Changes in invertase mobility were also followed in a time course both for immobilized and for freely suspended batch grown cells. Mobility of invertase from free cells increased an approximately 15 h of incubation, independently of the carbon source, whilst that of invertase from immobilized cells remained constant. The differences observed were attributed to a different level of glycosylation of the protein moiety in free and immobilized cells. The amount of mannnoproteins in the cell walls of immobilized cells was also investigated by ConA ferritin labelling and quantification of ferritin particle density in ultrathin sections; the results of this experiments showed a higher content of mannoproteins in the walls of immobilized cells when compared with free cells. As a whole, these results are indicative of physiological changes can be ascribed to the peculiar microenvironment of gel-immobilized cells