Subperoxisomal localization of glycolate oxidase

The subperoxisomal distribution of glycolate oxidase (GO) in leaves and cotyledons of several plants was investigated using post-embedding immunogold labelling. In peroxisomes with amorphous nucleoids, all of the immunolabelling is associated with the matrix of the peroxisome, even in tissue embedded in Lowicryl, a resin that preserves antigenicity best. This same staining pattern was found after cytochemical staining for GO activity with cerium. In peroxisomes with crystalline inclusions, the inclusions are only lightly labelled, compared with the densely-labelled matrix. Cytochemical reactions are noted between the units of the crystal in these peroxisome types. Because cytochemical reactions for catalase are concentrated in the amorphous nucleoid and crystalline peroxisomal inclusions, the general lack of immunogold staining of GO and other peroxisomal proteins indicate that catalase may be the major (or in some cases the exclusive) constituent of these peroxisomal inclusions.     

Subperoxisomal localization of glycolate oxidase

Summary The subperoxisomal distribution of glycolate oxidase (GO) in leaves and cotyledons of several plants was investigated using post-embedding immunogold labelling. In peroxisomes with amorphous nucleoids, all of the immunolabelling is associated with the matrix of the peroxisome, even in tissue embedded in Lowicryl, a resin that preserves antigenicity best. This same staining pattern was found after cytochemical staining for GO activity with cerium. In peroxisomes with crystalline inclusions, the inclusions are only lightly labelled, compared with the denselylabelled matrix. Cytochemical reactions are noted between the units of the crystal in these peroxisome types. Because cytochemical reactions for catalase are concentrated in the amorphous nucleoid and crystalline peroxisomal inclusions, the general lack of immunogold staining of GO and other peroxisomal proteins indicate that catalase may be the major (or in some cases the exclusive) constituent of these peroxisomal inclusions.     

Primary structure of glycolate oxidase from spinach

The primary structure of glycolate oxidase from spinach has been determined. Six different types of peptide digest were investigated, utilizing CNBr, proteolytic enzymes, and chemical modifications to change a specificity of cleavage. In total, 90 peptides were purified and analyzed. The studies were aimed at correlation with crystallographic analysis of the same protein carried through in parallel and with cDNA studies which utilized initially determined amino acid sequences for synthesis of oligonucleotide probes. Continuous comparisons with the results from the crystallographic studies helped at an early stage to secure peptide overlaps, at the same time as the peptide data secured residue assignments in the electron density maps. In the end, all data agree and regions from all parts of the molecule have been checked by independent methods of analysis. The primary structure establishes the type of N-terminal post-translational processing, and yields information on segments not fully defined in electron density maps. Combined, the chemical, crystallographic, and cDNA data give extensive reliability. The peptide analysis shows that the N-terminus is blocked by acylation of the initiator methionine, which is in a primary structure typical for non-removal of the methionine in the processing events of the nascent protein chain. The molecule is comparatively rich in menthionine and some other generally less common residues, but has only one cysteine residue and no extensive hydrophobic segment. An amino acid sequence homology with flavocytochrome b2 from yeast, as expected from known similarities in tertiary structure, is observed (33% residue identities).     

A peroxisomal glycolate oxidase in the algaMougeotia

Microbodies of the algaMougeotia were isolated in a linear sucrose gradient. The organelles, which moved to the density 1.24 g cm^–3, contained about 70% of the glycolate oxidase (EC 1.1.3.1) found in this alga. The enzyme oxidized glycolate, utilizing either oxygen or 2,6-dichlorophenolindophenol (DCPIP) as the electron acceptor. L-Lactate was an alternate substrate; almost no D-lactate was utilized. In the presence of O₂, a K_m of 415 M was determined for glycolate, whereas the K_m for L-lactate was about 5,000 M. In the presence of DCPIP, lower concentrations of glycolate and L-lactate were sufficient to obtain the highest rates of enzyme activity.Abbreviations DCPIP 2,6-dichlorophenolindophenol Supported by the Deutsche Forschungsgemeinschaft     

乙醇酸氧化酶基因在巴斯德毕赤氏酵母中的表达

将菠菜乙醇酸氧化酶基因片段克隆至表达载体pPIC3．5k。提取重组质粒,进行限制性酶切鉴定。重组质粒用Sal I酶切线性化,电导入法转化毕赤酵母(Pichia pastoris),在缺乏组氨酸的RDB平板筛选重组子,提取酵母的染色体基因组进行PCR扩增鉴定整合情况,用甲醇诱导表达。结果表明,SDS-PAGE电泳显示表达蛋白的分子量约为39．8kD,与文献报道的乙醇酸氧化酶分子量接近。酶的活力达到了40．8IU／g湿菌体,比不含有目的片断的对照菌酶活提高了17倍,确认了导入的乙醇酸氧化酶基因片段在酵母中高效表达。     

Permeabilization of Pichia pastoris for glycolate oxidase activity

Maximum activity of glycolate oxidase was obtained from a recombinant Pichia pastoris by permeabilization with 0.1% benzalkonium chloride for 60 min at room temperature. After treatment, intracellular glycolate oxidase activity increased 10-fold with respect to untreated cells.     

Identity of aliphatic L- -hydroxyacid oxidase and glycolate oxidase from rat livers

l-α-Hydroxyacid oxidase and glycolate oxidase have been partially purified from rat livers and found to be identical, judging by substrate specificities, K_m values for certain substrates and coenzyme (FMN), activation energy, inhibition rates by various reagents and pH optimum. K_m values are as follows; glycolate, 2.4 × 10^?4m; l-α-hydroxyisocaproate, 1.26 × 10^?3; glyoxylate, 1.41 × 10^?4m; and FMN, 1.13 × 10^?6m. K_m values for glycolate and FMN are one-tenth and one-twentieth the literature values for hepatic glycolate oxidase. Sucrose density gradient centrifugation establishes that this enzyme is located in hepatic peroxisomes.     

The occurrence of glycolate dehydrogenase and glycolate oxidase in green plants: an evolutionary survey

Homogenates of various lower land plants, aquatic angiosperms, and green algae were assayed for glycolate oxidase, a peroxisomal enzyme present in green leaves of higher plants, and for glycolate dehydrogenase, a functionally analogous enzyme characteristic of certain green algae. Green tissues of all lower land plants examined (including mosses, liverworts, ferns, and fern allies), as well as three freshwater aquatic angiosperms, contained an enzyme resembling glycolate oxidase, in that it oxidized l- but not d-lactate in addition to glycolate, and was insensitive to 2 mm cyanide. Many of the green algae (including Chlorella vulgaris, previously claimed to have glycolate oxidase) contained an enzyme resembling glycolate dehydrogenase, in that it oxidized d- but not l-lactate, and was inhibited by 2 mm cyanide. Other green algae had activity characteristic of glycolate oxidase and, accordingly, showed a substantial glycolate-dependent O₂ uptake. It is pointed out that this distribution pattern of glycolate oxidase and glycolate dehydrogenase among the green plants may have phylogenetic significance.     

A spectrophotometric method for the determination of glycolate in urine and plasma with glycolate oxidase

An enzymatic assay was developed for the spectrophotometric determination of glycolate in urine and plasma. Glycolate was first converted to glyoxylate with glycolate oxidase, and the glyoxylate formed was condensed with phenylhydrazine. The glyoxylate phenylhydrazone formed was then oxidized with K(3)Fe(CN)(6) in the presence of excess phenylhydrazine, and A(515) of the resulting 1, 5-diphenylformazan was measured. Since glycolate oxidase also acts on glyoxylate and L-lactate, the incubation of samples with glycolate oxidase was carried out in 120-170 mM Tris-HCl (pH 8.3) to obtain glyoxylate as its adduct with Tris. The pyruvate formed from lactate was removed by subsequent brief incubation with alanine aminotransferase in the presence of L-glutamate, and alpha-ketoglutarate formed was converted back to L-glutamate by glutamate dehydrogenase and an NADPH generating system. Thus the specificity of the assay relies principally on the substrate specificity of glycolate oxidase, and high sensitivity is provided by the high absorbance of 1,5-diphenylformazan at 515-520 nm. Plasma was deproteinized with perchloric acid, and then neutralized with KOH. Plasma and urine samples were then incubated with approximately 5 mM phenylhydrazine, and then treated with stearate-deactivated activated charcoal to remove endogenous keto and aldehyde acids as their phenylhydrazones. The normal plasma glycolate and urinary glycolate/creatinine ratio for adults determined by this method are approximately 8 microM and approximately 0.036, respectively.     

Cytochemical localization of glycolate oxidase in microbodies of Klebsormidium

The filamentous green alga Klebsormidium flaccidum A.Br. was fixed with glutaraldehyde, incubated in a cytochemical medium designed to detect glycolate-oxidase activity, and prepared for electron microscopy. Heavy deposits of stain were observed in microbodies following incubation with either glycolate or L-lactate as substrate, but not after incubation with D-lactate or H₂O. When Chlamydomanas reinhardi Dangeared cells were treated in the same way, their microbodies did not appear stained. The results establish that in Klebsormidium glycolate-oxidase occurs in microbodies (peroxisomes), as it does in angiosperms; also, they emphasize the dichotomy between those green algae which contain glycolate-oxidase and those, such as Chlamydomonas, which possess the mitochondrial enzyme glycolate dehydrogenase.     

Purification and characterization of glycolate oxidase from pumpkin cotyledons

Glycolate oxidase was purified and crystallized from cotyledons of germinating pumpkin seedlings. The molecular weight of the enzyme was determined to be 280,000-320,000, consisting of 8 identical subunits with molecular weight of 38,000. There are two absorption peaks at 340 and 450 nm, indicating the glycolate oxidase is a flavin protein. Several kinetic parameters were determined, Km (glycolate) 0.33 mM and Km (O2) 76.2 microM at pH 8.0. Oxalate and oxalacetate were found to be potent competitive inhibitors against glycolate; the Ki values for oxalate and oxalacetate were 4.5 and 7.8 mM, respectively. Fatty acids such as linoleic acid inhibited the enzyme noncompetitively; the Km for linoleic acid was 0.63 mM. The regulation of glycolate oxidase in the glycolate pathway occurring in leaf peroxisomes is discussed.     

Purification and characterization of recombinant human liver glycolate oxidase

Glycolate oxidase, an FMN-dependent peroxisomal oxidase, plays an important role in plants, related to photorespiration, and in animals, where it can contribute to the production of oxalate with formation of kidney stones. The best studied plant glycolate oxidase is that of spinach; it has been expressed as a recombinant enzyme, and its crystal structure is known. With respect to animals, the enzyme purified from pig liver has been characterized in detail in terms of activity and inhibition, the enzyme from human liver in less detail. We describe here the purification and initial characterization of the recombinant human glycolate oxidase. Its substrate specificity and the inhibitory effects of a number of anions are in agreement with the properties expected from previous work on glycolate oxidases from diverse sources. The recombinant enzyme presents an inhibition by excess glycolate and by excess DCIP, which has not been documented before. These inhibitions suggest that glycolate binds to the active site of the reduced enzyme, and that DCIP also has affinity for the oxidized enzyme. Glycolate oxidase belongs to a family of l-2-hydroxy-acid-oxidizing flavoenzymes, with strongly conserved active-site residues. A comparison of some of the present results with studies dealing with other family members suggests that residues outside the active site influence the binding of a number of ligands, in particular sulfite.     

Expression of active spinach glycolate oxidase in Aspergillus nidulans

The biocatalytic production of glyoxylic acid from glycolic acid requires two enzymes: glycolate oxidase, which catalyzes the oxidation of glycolic acid by oxygen to produce glyoxylic acid and hydrogen peroxide, and catalase, which decomposes the byproduct hydrogen peroxide. As an alternative to isolation from the leaf peroxisomes of spinach, glycolate oxidase has now been cloned and expressed in transformants of Aspergillus nidulans T580 at levels ranging from 1.7 to 36 IU/g dry wt. cells. The glycolate oxidase of transformant strain T17 comprises ca. 1.9% of total cell protein and is expressed at near 100% activity. (c) 1996 John Wiley & Sons, Inc.     

Luminometric determination of oxidase activity in peroxisomal fractions of rat liver: glycolate oxidase

The feasibility of using the H2O2-mediated chemiluminescence for determination of the activity of oxidases in peroxisomes of rat liver has been investigated. In an assay medium containing luminol, horseradish peroxidase, and azide with glycolate as substrate, a linear relationship is obtained between the amount of peroxisomal protein used and the luminescence signal. In comparison with other techniques available for measuring the activities of peroxisomal oxidases the luminometric approach described here is 5-10 times more sensitive than the spectrophotometric methods and 100 times more efficient than the polarographic determination of O2. Under the optimal assay conditions the glycolate oxidase activity can be determined in amounts as low as 0.5 micrograms peroxisomal protein.     

Preliminary crystallographic data for glycolate oxidase from spinach.

Glycolate oxidase, an enzyme that plays an important role in photorespiration in plants, has been purificant from spinach and crystallized in two different crystal forms. Form A which was obtained with tertiary butanol as precipitating agent belongs to space group I 422 with unit cell dimensions a = b = 148.1 A and c = 134.9 A. This form diffracts to high resolution and will be used for further crystallographic studies. Form B is also tetragonal, space group P42212, with cell dimensions a = b = 145.4 A and c = 104.2 A. This form was obtained from ammonium sulfate precipitations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis shows that the enzyme is built up from subunits of molecular weight 37,000. The asymmetric units of both crystal forms contain at least two such subunits.