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At least 163 records · Page 9Linked to original sources
PubMed1995

Function of N-terminal import signals in trypanosome microbodies.

The glycosomes of trypanosomes are related to eukaryotic peroxisomes. For many glycosomal and peroxisomal proteins, a C-terminal SKL-like tripeptide known as PTS-1 serves as the targeting signal. For peroxisomes, a second N-terminal signal (PTS-2) was demonstrated on rat 3-ketoacyl-CoA thiolase. Several glycosomal proteins do not bear a PTS-1. One such protein, fructose bisphosphate aldolase, has a PTS-2 homology at its N-terminus. To find out whether the PTS-2 pathway exists in trypanosomes, we expressed chloramphenicol acetyltransferase fusion proteins bearing N-terminal segments of either rat thiolase or trypanosome aldolase. The mammalian PTS-2 clearly mediated glycosomal import. The aldolase N-terminus mediated import with variable efficiency depending on the length of the appended sequence. These results provide evidence for the existence of the PTS-2 pathway in trypanosomes.

Acetyl-CoA C-Acetyltransferase↗
PubMed1984

A comparison of the glycosomes (microbodies) isolated from Trypanosoma brucei bloodstream form and cultured procyclic trypomastigotes.

Highly purified glycosomes were isolated from Trypanosoma brucei bloodstream forms and cultured procyclic trypomastigotes. A comparison of the specific activities of glycosomal enzymes revealed that glycosomes from insect stages had decreased levels of hexokinase, phosphoglucose isomerase, phospho-fructokinase, fructose-bisphosphate aldolase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase, but contained increased levels of adenylate kinase, malate dehydrogenase and phosphoenolpyruvate carboxykinase. Glycosomes from bloodstream forms were almost totally devoid of the latter two activities. Comparison of the two types of glycosomes by sodium dodecylsulphate-polyacrylamide gel electrophoresis revealed that bloodstream form glycosomes contained 3 prominent polypeptides (64, 46 and 40 kDa) which were hardly detectable in insect stage glycosomes, whereas the latter contained 3 insect stage specific bands with molecular weight of 34 000, 61 000 and 77 000 and 4 additional bands with molecular weights between 94 000 and 110 000. Both types of glycosome contained the phospholipids phosphatidylcholine and phosphatidylethanolamine. Insect stage glycosomes contained in addition also phosphatidylinositol and some phosphatidylserine.

Animals↗
PubMed1984

The occurrence of glycosomes (microbodies) in the promastigote stage of four major Leishmania species.

Evidence is presented for the occurrence of glycosomes (organelles resembling peroxisomes) in four major species of Leishmania (viz. L. major, L.m. mexicana, L. b. braziliensis and L. donovani), based on latency as well as differential and isopycnic centrifugation studies. The enzymes involved in glycolysis; (hexokinase, phosphoglucose isomerase, phosphofructokinase, fructose-1,6-bisphosphate aldolase, triosephosphate isomerase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase); glycerol metabolism (sn-glycerol-3-phosphate dehydrogenase and glycerol kinase); carbon dioxide fixation (phosphoenolpyruvate carboxykinase and possibly malate dehydrogenase); together with an enzyme involved in the beta-oxidation of fatty acids (3-beta-hydroxybutyryl coenzyme A dehydrogenase); a key enzyme in the synthesis of ether lipids (dihydroxyacetone phosphate acyltransferase) as well as the ADP utilising enzyme adenylate kinase, were all found associated, at least in part, with a subcellular organelle which had a buoyant density in sucrose gradients of 1.21 to 1.24 g cm-3. Little variance in enzyme composition was found between the different species of Leishmania or in comparison with other members of the Trypanosomatidae, supporting the unifying principle that glycosomes are a unique characteristic of this family. The occurrence of important catabolic, anabolic and anaplerotic pathways in the glycosomes of Leishmania renders them prime targets for chemotherapy.

Animals↗
PubMed2003

Changes in some enzymes of microbodies and plastid development in excised radish cotyledons: effect of narciclasine.

Narciclasine (NCS), isolated from mucilage of Narcissus bulb, showed inhibitory effects on growth and plastid development of excised radish cotyledons. NCS (0.1 mumol/L) started to show inhibitory effects on isocitrate lyase and hydroxypyruvate reductase activities after 24 h incubation in light. When NCS concentration was increased to 10 mumol/L, the activities of both enzymes are completely inhibited. From ultrastructural studies, NCS markedly prevented the degradation of protein bodies and lipid bodies, as well as chloroplast formation of excised radish cotyledons. There was only little degradation of protein and lipid bodies, and almost no chloroplast formation in the excised radish cotyledon treated with 1 mumol/L NCS. Therefore, our results provide clear evidence that NCS inhibited the transition of glyoxysomes and peroxisomes, and chloroplast development.

Alcohol Oxidoreductases↗
PubMed1978

Plant microbody proteins. Purification and glycoprotein nature of glyoxysomal isocitrate lyase from cucumber cotyledons.

1. Isocitrate lyase from cotyledons of cucumber seedlings (Cucumis sativus) has been purified 100-fold. Two methods of preparing the soluble glyoxylate cycle enzyme are described: an elaborated method which used crude extracts of cucumber cotyledons, and another procedure which started with purified glyoxysomes from 4-day-old cotyledons and included a separation of glyoxysomal matrix enzymes by zonal centrifugation. The product behaved as a single species when tested by (a) polyacrylamide gel electrophoresis in the presence of dodecyl sulfate, (b) zonal centrifugation, and (c) double immunodiffusion against rabbit antibody to isocitrate lyase. 2. Isocitrate lyase of cucumber glyoxysomes exhibited a molecular weight of 255,000 and was composed of four apparently identical subunits of Mr 64,000. An isoelectric point of 5.9 was determined. 3. It was shown that isocitrate lyase is a glycoprotein, (a) by Schiff stain on polyacrylamide gels, (b) by periodate oxidation of the enzyme, subsequent reduction with NaB[3H]4 and electrophoretic analysis of the labelled glycoprotein, and (c) by incorporation of [3H]glucosamine in vivo into a protein which could be precipitated with antibodies to isocitrate lyase and revealed a 64,000-Mr band upon electrophoresis.

Carbohydrates↗