Cyst Wall Protein Synthesis and Some Enzyme Changes on Starvation and Encystment in Colpoda steinii

Publisher Website
Google Scholar
Abstract
SYNOPSIS. During starvation‐induced encystment, Colpoda steinii loses some 30% of its nitrogen before synthesizing a glutamic acid‐rich protein coat, which after 24 hr accounts for 18% of the cyst protein. Settling cells contain 29 ± 2 pg/cell of glutamic acid (free acid plus that released on hydrolysis) whilst encysted cells contain 51 ± 3 pg/cell, the coat glutamic acid being adequate to account for the increase. Thus substantial glutamic acid and protein biosynthesis occur during starvation. Assayed in homogenates, some relevant enzymes appeared to decrease rather than increase in activity as encystment proceeded. Intra‐cellular proteolytic activity showed little alteration but ribonuclease, acid phosphatase, L‐alanine: 2‐oxoglutarate aminotransferase (E.C.2.6.1.2) and L‐glutamate:NAPD oxidoreductase (E.C.1.4.1.4) were considerably reduced. The total carbohydrate content of the cell also increased during starvation.