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

Abstract

The intracellular distribution of enzymes capable of catalyzing the reactions from phosphoglycolate to glycerate in the bluegreen colored eucaryotic alga Cyanidium caldarium has been studied. After separating the organelles from a crude homogenate on a linear flotation gradient, the enzymes glycolate oxidase and glutamate-glyoxylate aminotransferase along with catalase were present in the peroxisomal fraction (density: 1.23 grams per cubic centimeter). Serine hydroxymethyltransferase was found in the mitochondrial fraction (density: 1.18 grams per cubic centimeter). In contrast to the observations in green leaves of higher plants, the enzymes for the conversion of serine to glycerate (serineglyoxylate aminotransferase and hydroxypyruvate reductase) were found only in the soluble fraction of the gradient. The partial characterization of enzymes from Cyanidium participating in glycolate metabolism revealed only slight differences from the corresponding enzymes from higher plants. The phylogenetic implications of the observed similarities between the enigmatic alga Cyanidium and higher plants are discussed.

Identification and Characterization of Glycolate Oxidase and Related Enzymes from the Endocyanotic Alga Cyanophora paradoxa and from Pea Leaves

“…The finding that there are important differences in the kinetic properties of GOs from Cyanophora, other algae (15)(16)(17)31) Figure 3 suggest, however, that Cyanophora has an enzyme similar to the recently identified cytoplasmic NADPH/NADH hydroxypyruvate reductase in spinach leaves (23). This leaf enzyme is also prone to substrate inhibition and is more active with hydroxypyruvate than with glyoxylate (see Fig.…”

“…Cyanidium caldarium can also be considered as a cyanome and GO was identified in this alga. The catalytic properties of Cyanidium toward hydroxypyruvate and glyoxylate are, however, clearly different from those of Cyanophora (16) (Table III). Unlike leaf peroxisomal NADH-hydroxypyruvate reductase, the Cyanophora enzyme was markedly inhibited by hydroxypyruvate concentrations above 0.5 mM with NADH as a cosubstrate (Fig.…”

“…This enzyme is associated with mitochondrial membranes or the lamellae (10,27). In Charophyceae and leaves, glycolate is oxidized by peroxisomal GO (15,20,32), and recently, GO was reported to occur in other algal groups also (16,17,31). GO has been distinguished from GD on the basis of the following criteria: (a) GD is inhibited by CN-(2 mM), (b) GD can convert D-lactate; whereas GO is not inhibited by CN-and can convert L-lactate (15); (c) isolated GO can directly use 02 as an electron acceptor and forms H202; whereas GD requires an intermediate electron acceptor (15,27) and does not produce H202; (d) GD in cell homogenates can readily reduce the artificial electron acceptor DCPIP in the presence of 02; whereas the DCPIP reductase activity of isolated GO is inhibited by 02 (13,15).…”

Glyceraldehyde 3-Phosphate:NADP+ Reductase of Spinach Leaves

“…The importance of GNR as an NADPH-producing enzyme in the cytosol is more readily understood for specialized biosynthetic tissues (4, 18) than for normal leaves, although these are a general source of export metabolites (24). However, hydroxypyruvate reductase is partly cytosolic and NADPH-dependent (14,20), and the NADPH produced by GNR could act as a photorespiratory reductant. GNR is absent from bundle sheath cells of maize (28), which are deficient in triose phosphate production and photorespiration.…”

PURIFICATION AND CHARACTERIZATION OF GLYCOLATE OXIDASE FROM THE BROWN ALGA SPATOGLOSSUM PACIFICISM (PHAEOPHYTA)1

“…On the other hand, glycolate oxidase has been found in all classes of the Chromophyta (Gross et al 1985, Gross 1990 1) except the Bacillariophyceae (Paul andVol-cani 1974, Suzuki et al 1991). Glycolate oxidase has also been found in the unicellular red alga Porphyridium purpureurn (Suzuki et al 199 l), the primitive red alga Cyanidium caldarium (Gross and Beevers 1989), and the endocyanotic alga Cyanophora paradoxa (Betsche et al 1992).…”