Characterization of Peroxisomes from the Alga Bumilleriopsis filiformis

Abstract

The Xa"thophycean alp Bumilkropsis filiformis possesses peroxisomes which on electron micrographs show a mostly spherical or ovoid shape with a diameter in the range of 03 micrometer. Their Microbodies have been demonstrated by electron microscopy to be present in many different algae (18), but only from a few of those organisms could the microbodies be isolated for biochemical characterization. Nevertheless, it has already become evident that there are different types ofalgal microbodies (7, 23).In Spirogyra and Mougeotia the peroxisomes are of the leaf type and are therefore involved in glycolate metabolism (22,25,30). On the other hand, the peroxisomes of the unicellular algae Chlorogonium, Chlamydomonas, ,Eremosphaera, and Polytomella contain neither enzymes of the glycolate metabolism nor enzymes ofthe glyoxylic acid cycle (6,20,21,24,27). Thus, they have been regarded as unspecialized organelles.Until now algal microbodies of the glyoxysomal type have been isolated only from heterotrophically grown Euglena (1 1). Under autotrophic conditions, the corresponding organelles of this alga like leaf peroxisomes contain enzymes of glycolate metabolism (5). But these microbodies differ from leaf peroxisomes in that they contain a glycolate dehydrogenase rather than a glycolate oxidase (4, 16). Furthermore, there are also contrary reports whether catalase is a constituent of the organelles in Euglena (3,14,29).Recently it was reported that the unspecialized peroxisomes from Eremosphaera and the leaftype organelles from Mougeotia both contain enzymes of the #-oxidation pathway (28). Considering also the data for higher plants (8,9), it appeared that the possession of enzymes for the a-oxidation is a characteristic of ' Supported by the Deutsche Forschungsgemeinschaft.all different types of microbodies. This assumption now seems to be questionable since we have isolated peroxisomes from the Xanthophycean alga Bumilleriopsis which could not be demonstrated to contain enzymes for degradation of fatty acids. MATERIALS AND METHODSAlgal Material and Growth Conditions. Bumilleriopsisfiliformis (Xanthophyceae), strain 802-2, was obtained from the algae collection of the Institute for Plant Physiology, University of Gottingen, W. Germany.Cultures were grown autotrophically in glass tubes at 23YC in continuous light ofeither 3,000 or 20,000 lux in nutrient medium (12). The cultures were aerated with air plus 2% CO2 or air only.Preparation of Cell Homogenates and Separation of Organelles. Cells of 1 L of suspension were collected by low speed centrifugation and washed with grinding medium (28). For homogenization, the cells were transferred to 20 ml of the same medium containing 100 mg Polyclar AT, 20 mg cystein, 15 mg DTT, 70 mg BSA, and 15% (w/w) sucrose. Cells were broken in a Virtis homogenizer after adding 30 ml glass beads; the homogenate was centrifuged at 5OOg for 10 min. The resulting supernatant was used for sucrose density centrifugation (28).Assays. All assays for measuring the activities ofenzymes were ...

Subcellular Distribution of Enzymes of Glycolate Metabolism in the Alga Cyanidium caldarium

“…In the Xanthophyte Bumilleriopsis another variation of this pathway was observed. This alga possesses a glycolate oxidase, but the second key enzyme, hydroxypyruvate reductase, is absent ( 13).…”

“…This is certainly true for the Chlorophytes, Bacillariophytes, and Euglenophytes (12), but recent studies have shown that in Charophytes (27), Xanthophytes (13), and Cyanophora (3) a glycolate oxidase is present. The finding that the enigmatic alga Cyanidium also possesses a glycolate oxidase suggests that among the algae a glycolate oxidase is more widespread than previously assumed.…”

Intracellular Localization of Enzymes of Fatty Acid-β-Oxidation in the Alga Cyanidium caldarium

“…In the chlorophyte Eremosphaera viridis (33) and in four Prasinophycean algae (29), a dual localization has been found similar to the situation in mammalian tissue. A solely mitochondrial location is present in the xanthophyte Bumilleriopsisfiliformis (14). (The results reported by Graves and Becker [12] on the distribution of f-oxidation enzymes in heterotrophically grown Euglena are not conclusive.)…”

“…Although only a few algae have been examined, it is already clear that, in contrast to the consistent picture observed within mammalian and higher plant groups respectively, several dispositions of the enzymes of 1-oxidation occur within this single group. An exclusively peroxisomal location has been found in the charophyte Mougeotia (28), a dual site of 1-oxidation in the chlorophyte Eremosphaera (33) as well as in several Prasinophytes (29) and a mitochondrial location in the xanthophyte Bumilleriopsis (14) and in Cyanidium. Such differences may have taxonomic value.…”

“…Enzymes were tested as described: catalase, aldolase, alcohol dehydrogenase, a-amylase, peroxidase, hexokinase, malate dehydrogenase (2), fumarase (5), citrate synthase (15), glycolate oxidase, formation ofphenylhydrazone (14), thiolase (33), enoyl-CoA hydratase, hydroxyacyl-CoA dehydrogenase (28), carnitine palmitoyltransferase, carnitine acetyltransferase (3), acyl-CoA oxidoreductase (6,28), acyl-CoA oxidase (18), Cyt c oxidase, NADPH-Cyt c reductase (17). The Three enzymes of /3-oxidation tested-enoyl-CoA hydratase, HOA-DH, and thiolase-exhibit an activity peak in the gradient coinciding with that of citrate synthetase and fumarase.…”