Biogenesis of Glycosomes (Microbodies) in the Trypanosomatidae

Abstract

Glycosomes, the microbodies of Trypanosomatid haemoflagellates, contain several enzymes involved in glucose and glycerol metabolism. Enzymes such as glyceraldehyde-phosphate dehydrogenase, aldolase and glycerol-3-phosphate dehydrogenase are synthesized in the cytosol on free polyribosomes as polypeptides of mature size. They remain in the cytosol with a half-life of 3 min, while in the glycosome the three enzymes turn over with a half-life of less than 1 h. Most glycosomal enzymes have an apparent M which is 1–5 kDa larger than their homologous counterparts from the cytosol or from other organisms and are highly basic proteins. It is proposed that the topogenic signal responsible for import into the glycosome is integral and consists of unique insertions in the polypeptide chain which give rise to an additional positive charge to the protein