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At least 19 recordsLinked to original sources
PubMed1992

Substrate specificities of rat liver peroxisomal acyl-CoA oxidases: palmitoyl-CoA oxidase (inducible acyl-CoA oxidase), pristanoyl-CoA oxidase (non-inducible acyl-CoA oxidase), and trihydroxycoprostanoyl-CoA oxidase.

Rat liver peroxisomes contain three acyl-CoA oxidases:palmitoyl-CoA oxidase, pristanoyl-CoA oxidase, and trihydroxycoprostanoyl-CoA oxidase. The three oxidases were separated by anion-exchange chromatography of a partially purified oxidase preparation, and the column eluate was analyzed for oxidase activity with different acyl-CoAs. Short chain mono (hexanoyl-) and dicarboxylyl (glutaryl-)-CoAs and prostaglandin E2-CoA were oxidized exclusively by palmitoyl-CoA oxidase. Long chain mono (palmitoyl-) and dicarboxylyl (hexadecanedioyl-)-CoAs were oxidized by palmitoyl-CoA oxidase and pristanoyl-CoA oxidase, the former enzyme catalyzing approximately 70% of the total eluate activity. The very long chain lignoceroyl-CoA was also oxidized by palmitoyl-CoA oxidase and pristanoyl-CoA oxidase, the latter enzyme catalyzing approximately 65% of the total eluate activity. Long chain 2-methyl branched acyl-CoAs (2-methylpalmitoyl-CoA and pristanoyl-CoA) were oxidized for approximately 90% by pristanoyl-CoA oxidase, the remaining activity being catalyzed by trihydroxycoprostanoyl-CoA oxidase. The short chain 2-methylhexanoyl-CoA was oxidized by trihydroxycoprostanoyl-CoA oxidase and pristanoyl-CoA oxidase (approximately 60 and 40%, respectively, of the total eluate activity). Trihydroxycoprostanoyl-CoA was oxidized exclusively by trihydroxycoprostanoyl-CoA oxidase. No oxidase activity was found with isovaleryl-CoA and isobutyryl-CoA. Substrate dependences of palmitoyl-CoA oxidase and pristanoyl-CoA oxidase were very similar when assayed with the same (common) substrate. Since the two oxidases were purified to a similar extent and with a similar yield, the contribution of each enzyme to substrate oxidation in the column eluate probably reflects its contribution in the intact liver.

Acyl Coenzyme A↗
PubMed1990

Presence of three acyl-CoA oxidases in rat liver peroxisomes. An inducible fatty acyl-CoA oxidase, a noninducible fatty acyl-CoA oxidase, and a noninducible trihydroxycoprostanoyl-CoA oxidase.

Mammalian liver peroxisomes are capable of beta-oxidizing a variety of substrates including very long chain fatty acids and the side chains of the bile acid intermediates di- and trihydroxycoprostanic acid. The first enzyme of peroxisomal beta-oxidation is acyl-CoA oxidase. It remains unknown whether peroxisomes possess one or several acyl-CoA oxidases. Peroxisomal oxidases from rat liver were partially purified by (NH4)2SO4 precipitation and heat treatment, and the preparation was subjected to chromatofocusing, chromatography on hydroxylapatite and dye affinity matrices, and gel filtration. The column eluates were assayed for palmitoyl-CoA and trihydroxycoprostanoyl-CoA oxidase activities and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results revealed the presence of three acyl-CoA oxidases: 1) a fatty acyl-CoA oxidase with a pI of 8.3 and an apparent molecular mass of 145 kDa. The enzyme consisted mainly of 52- and 22.5-kDa subunits and could be induced by clofibrate treatment; 2) a noninducible fatty acyl-CoA oxidase with a pI of 7.1 and an apparent molecular mass of 427 kDa. It consisted mainly, if not exclusively, of one polypeptide component of 71 kDa; and 3) a noninducile trihydroxycoprostanoyl-CoA oxidase with a pI of 7.1 and an apparent molecular mass of 139 kDa. It consisted mainly, if not exclusively, of one polypeptide component of 69 kDa. Our findings are probably related to the recent discovery of two species of acyl-CoA oxidase mRNA in rat liver (Miyazawa, S., Hayashi, H., Hijikata, M., Ishii, N., Furata, S., Kagamiyama, H., Osumi, T., and Hashimoto, T. (1987) J. Biol. Chem. 262, 8131-8137) and they probably also explain why in human peroxisomal beta-oxidation defects an accumulation of very long chain fatty acids is not always accompanied by an excretion of bile acid intermediates and vice versa.

Acyl-CoA Oxidase↗
PubMed1981

Rotation of cytochrome oxidase in phospholipid vesicles. Investigations of interactions between cytochrome oxidases and between cytochrome oxidase and cytochrome bc1 complex.

Cytochrome oxidase was incorporated into lipid vesicles composed of phosphatidylethanolamine-phosphatidylcholine-cardiolipin. Large proteoliposomes of 1,000-15,000 A diameter were prepared by calcium-induced fusion of small vesicles. Rotational diffusion of cytochrome oxidase was measured by detecting the decay of the absorption anisotropy, r(t), after photolysis of the heme a3.CO complex by a vertically polarized laser flash. Because of the large size of the proteoliposomes, there was no contribution of vesicle-tumbling to r(t) over the experimental time range of 5 ms for samples in 60% sucrose. Analysis of r(t) curves was based on a "rotation-about-membrane normal" model. The measurements were used to investigate intermolecular interactions between cytochrome oxidases and between cytochrome oxidase and cytochrome bc1 complex co-reconstituted in the above lipid vesicles. In vesicles of a high lipid to protein ratio (congruent to 27), nearly all cytochrome oxidase molecules are rotating with an approximate rotational relaxation time, phi 1, on the order of 500 microseconds. In contrast, about 20% of cytochrome oxidase is immobile in vesicles with a relatively low lipid to protein ratio (congruent to 5), although phi 1 of the mobile population remains about 500 microseconds. In contrast, about 20% of cytochrome oxidase is immobile in vesicles with a relatively low lipid to protein ratio (congruent to 5), although phi 1 of the mobile population remains about 500 microseconds. The immobilized fraction is presumably due to nonspecific self-aggregation of cytochrome oxidase. The presence of cytochrome bc1 complex does not change r(t) curves significantly, either in the presence or absence of cytochrome c. Previously, we have observed the co-existence of mobile and immobile populations of cytochrome oxidase in bovine heart and rat heart mitochondria (Kawato, S., Sigel, E., Carafoli, E., and Cherry, R. J. (1980) J. Biol. Chem. 255, 5508-5510). The present results suggest that the immobile population of about one-half of cytochrome oxidase could be simply due to nonspecific protein aggregation resulting from the high concentration of enzymes in the inner mitochondrial membrane (lipid to protein ratio, less than or equal to 0.5). We also conclude that there is no specific interaction between cytochrome oxidase and cytochrome bc1 complex in the above large lipid vesicles. A lateral collision-controlled model for electron transfer from cytochrome bc1 complex to cytochrome oxidase through cytochrome c is discussed based on the above results.

Animals↗
PubMed2000

The human L-pipecolic acid oxidase is similar to bacterial monomeric sarcosine oxidases rather than D-amino acid oxidases.

L-Pipecolic acid oxidase activity is deficient in patients with peroxisome biogenesis disorders (PBDs). Because its role, if any, in these disorders is unknown, the authors cloned the human gene to order to further study its functions. BLAST search of the translated sequence showed greatest homology to Bacillus sp. NS-129 monomeric sarcosine oxidase. The purified enzyme could use either L-pipecolic acid or sarcosine as a substrate. No homology was found to the peroxisomal D-amino acid oxidases. A further comparison of L-pipecolic acid oxidase to the two D-amino acid oxidases in peroxisomes showed that the proteins differed in many ways. First, both D-amino acid oxidase and L-pipecolic acid oxidase showed no enzyme activity in liver from Zellweger syndrome patients; D-aspartate oxidase activity was unchanged from control levels. Although all were targeted to peroxisomes, their targeting signals differed. No L-pipecolic acid oxidase was found in brain or other tissues outside of liver and kidney. The D-amino acid oxidases were similarly and more widely distributed. Finally, although D-amino acid degradation is limited to peroxisomes in mammals, L-pipecolic acid can be oxidized in either mitochondria or peroxisomes, or both.

Bacillus↗
PubMed1981

Metabolism of acetylpolyamines by monoamine oxidase, diamine oxidase and polyamine oxidase.

N1-Monoacetylspermine, N1,N12-diacetylspermine and N1-monoacetylspermidine were found to be good substrates for rat liver polyamine oxidase, but not for rat liver mitochondrial monoamine oxidase. N8-Monoacetylspermidine, monoacetylcadaverine, monoacetylputrescine and monoacetyl-1,3-diaminopropane were oxidized by the monoamine oxidase when the substrate concentration was 10.0 mM, but not by the polyamine oxidase. All the acetylpolyamines except N1,N12-diacetylspermine were also oxidized by hog kidney diamine oxidase although their affinities for the oxidase appeared low. The present data suggest that acetylpolyamines are not easily metabolized in vivo by either monoamine oxidase or diamine oxidase in mammalian tissues although N1-monoacetylspermine, N1,N12-diacetylspermine and N1-monoacetylspermidine are attacked by polyamine oxidase.

Amine Oxidase (Copper-Containing)↗
PubMed1980

Separation of putrescine oxidase and spermidine oxidase in foetal bovine serum with the aid of a specific radioactive assay of spermidine oxidase.

1. A sensitive and specific assay for spermidine oxidase is described. The method involves the separation of [14C]spermidine (substrate) from [14C]putrescine (product) and other 14C-labelled products on a Dowex 50 cation-exchange column: 92% of the putrescine applied to the column was eluted by 2.3 M-HCl, but this treatment left 96% of the spermidine bound to the column. Unchanged spermidine could be removed from the column by elution with 6 M-HCl. 2. By means of this assay, foetal and adult bovine serum were each shown to contain spermidine oxidase activity, putrescine being a major product of the oxidation of spermidine by the serum enzymes. 3. In foetal bovine serum, spermidine oxidase activity is separable from putrescine oxidase activity by chromatography on a cadaverine-Sephadex column, by gel filtration and by ion-exchange column chromatography. Putrescine oxidase was purified 1900-fold and spermidine oxidase 130-fold by these procedures. The former oxidized putrescine but not spermidine, and spermidine oxidase exhibited no activity with putrescine as substrate.

Animals↗
PubMed1993

Identity of the axial ligand of the high-spin heme in cytochrome oxidase: spectroscopic characterization of mutants in the bo-type oxidase of Escherichia coli and the aa3-type oxidase of Rhodobacter sphaeroides.

Prokaryotic and eukaryotic cytochrome c oxidases and several bacterial ubiquinol oxidases compose a superfamily of heme-copper oxidases. These enzymes are terminal components of aerobic respiratory chains, the principal energy-generating systems of aerobic organisms. Two such heme-copper oxidases are the aa3-type cytochrome c oxidase of Rhodobacter sphaeroides and the bo-type ubiquinol oxidase of Escherichia coli. These enzymes catalyze the reduction of oxygen to water at a heme-copper binuclear center. Energy conservation is accomplished by coupling electron transfer through the metals of the oxidases to proton translocation across the cellular membrane. The Rb. sphaeroides and E. coli enzymes have previously been utilized in site-directed mutagenesis studies which identified two histidines which bind the low-spin heme (heme a), as well as additional histidine residues which are probable ligands for copper (CuB). However, the histidine that binds the heme of the binuclear center (heme a3) could not be unequivocally identified between two residues (His284 and His419). Additional characterization by Fourier transform infrared spectroscopy of the CO-bound forms of the E. coli enzyme in which His284 is replaced by glycine or leucine demonstrates that these mutations cause only subtle changes to CO bound to the heme of the binuclear center. Resonance Raman spectroscopy of the Rb. sphaeroides enzyme in which His284 is replaced by alanine shows that the iron-histidine stretching mode of heme a3 is maintained, in contrast with the loss of this mode in mutants at His419. These results demonstrate that His284 is not the heme a3 ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1999

Defining the structural domain of subunit II of the heme-copper terminal oxidase using chimeric enzymes constructed from the Escherichia coli bo-type ubiquinol oxidase and the thermophilic Bacillus caa(3)-type cytochrome c oxidase.

To probe the location of the quinol oxidation site and physical interactions for inter-subunit electron transfer, we constructed and characterized two chimeric oxidases in which subunit II (CyoA) of cytochrome bo-type ubiquinol oxidase from Escherichia coli was replaced with the counterpart (CaaA) of caa(3)-type cytochrome c oxidase from thermophilic Bacillus PS3. In pHNchi5, the C-terminal hydrophilic domain except a connecting region as to transmembrane helix II of CyoA was replaced with the counterpart of CaaA, which carries the Cu(A) site and cytochrome c domain. The resultant chimeric oxidase was detected immunochemically and spectroscopically, and the turnover numbers for Q(1)H(2) (ubiquinol-1) and TMPD (N,N, N',N'-tetramethyl-p-phenylenediamine) oxidation were 28 and 8.5 s(-1), respectively. In pHNchi6, the chimeric oxidase was designed to carry a minimal region of the cupredoxin fold containing all the Cu(A) ligands, and showed enzymatic activities of 65 and 5.1 s(-1), and an expression level better than that of pHNchi5. Kinetic analyses proved that the apparent lower turnover of the chimeric enzyme by pHNchi6 was due to the higher K(m) of the enzyme for Q(1)H(2) (220 microM) than that of cytochrome bo (48 microM), while in the enzyme by pHNchi5, both substrate-binding and internal electron transfer were perturbed. These results suggest that the connecting region and the C-terminal alpha(1)-alpha(2)-beta(11)-alpha(3) domain of CyoA are involved in the quinol oxidation and/or physical interactions for inter-subunit electron transfer, supporting our previous proposal [Sato-Watanabe, M., Mogi, T., Miyoshi, H., and Anraku, Y. (1998) Biochemistry 37, 12744-12752]. The close relationship of E. coli quinol oxidases to cytochrome c oxidase of Gram-positive bacteria like Bacillus was also indicated.

Amino Acid Sequence↗
PubMed1977

Platelet monoamine oxidase, plasma benzylamine oxidase and liver mixed function oxidase in cirrhotic patients.

Because it has been suggested that an accumulation of false neurochemical transmitters plays a part in the cardiovascular and neurological complications of cirrhosis it appeared worthwhile to study the level of monoamine oxidase in the liver and platelets of cirrhotic patients. In fact a decrease of such activities might explain the increase of false neurotransmitters observed in cirrhotic patients. Other enzyme were also tested: the plasma benzylamine oxidase activity and the liver mixed function oxidases. 13 cases of severe cirrhosis (B, C according to Child classification) and 10 cases of less severe cirrhosis (A according to Child classification) were studied in comparison to patients affected by cholelithiasis. A defect in the level of monoamine oxidase activity of platelets and liver was observed in some cirrhotic patients together with a decrease of the level of the liver mixed function oxidases.

Adult↗
PubMed1990

Methylamine oxidase from Arthrobacter P1 as a prototype of eukaryotic plasma amine oxidase and diamine oxidase.

Methylamine oxidase (MAOx) from Gram-positive soil bacterium Arthrobacter P1 catalyzes the oxidation of CH3NH2 to H2C = O and NH4+ via reduction of O2 to H2O2. Past work indicates that MAOx is similar to mammalian plasma amine oxidase (PAO) and diamine oxidase (DAO), plant DAO, and yeast peroxisomal amine oxidase (YAO). All have Mr congruent to 170,000 and are composed of 2 identical subunits, each of which contains 1 atom of Cu(II) and one molecule of quinonoid cofactor. Herein, we report further evidence as to the striking similarity of these enzymes, and describe properties of MAOx which offer insights into understanding the eukaryotic oxidases. It is our belief that the structure of the quinone cofactor, and the Cu(II) site in MAOx are identical to these sites in PAO and DAO.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Cytosolic guanine nucleotide-binding protein Rac2 operates in vivo as a component of the neutrophil respiratory burst oxidase. Transfer of Rac2 and the cytosolic oxidase components p47phox and p67phox to the submembranous actin cytoskeleton during oxidase activation.

The respiratory burst oxidase is responsible for O2- production in stimulated neutrophils and B lymphocytes. Components of this oxidase include cytochrome b558, a membrane-bound flavohemoprotein; the cytosolic polypeptides p47phox and p67phox; and one or more small G proteins including Rac1, Rac2, and/or Rap1A. We found that when normal neutrophils were activated, small percentages of each of the cytosolic proteins p47phox, p67phox, and Rac2 were transferred to the membrane cytoskeleton. However, Rac2 was not transferred to the membrane during activation of p47phox-deficient neutrophils. In normal cells, some p47phox also became associated with the non-cytoskeletal portion of the plasma membrane, but p67phox, Rac2, and O(2-)-forming activity were restricted to the cytoskeleton. Neutrophil activation also causes the phosphorylation of multiple serines in p47phox. The most heavily phosphorylated forms of p47phox were found solely in the membrane cytoskeleton. These results suggest that 1) the membrane cytoskeleton participates in respiratory burst oxidase activation, 2) the fully phosphorylated p47phox is located in the active oxidase, which resides in the membrane cytoskeleton, and 3) Rac2 acts like a dedicated component of the respiratory burst oxidase.

Actins↗
PubMed1985

Mechanism of action of methanol oxidase, reconstitution of methanol oxidase with 5-deazaflavin, and inactivation of methanol oxidase by cyclopropanol.

Methanol oxidase isolated from Hansenula polymorpha contains two distinct flavin cofactors in approximately equal amounts. One has been identified as authentic FAD and the other as a modified form of FAD differing only in the ribityl portion of the ribityldiphosphoadenosine side chain. The significance of this finding is as yet unknown. Previous studies have shown that cyclopropanol irreversibly inactivates methanol oxidase [Mincey, T., Tayrien, G., Mildvan, A. S., & Abeles, R. H. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 7099-7101]. We have now established that inactivation is accompanied by covalent modification of the flavin cofactor. The stoichiometry of this reaction is 1 mol of cyclopropanol/mol of active flavin. The structure of the covalent adduct was determined by NMR, IR, and UV spectral studies to be an N5,C4a-cyclic 4a,5-dihydroflavin. Reduction of the covalent adduct with NaBH4 at pH 9.0 before removal from the enzyme converted it to the 1-(ribityldiphosphoadenosine)-substituted 4-(3-hydroxypropyl)-2,3-dioxoquinoxaline. Cyclopropyl ring cleavage accompanies inactivation, and covalent bond formation occurs between a methylene carbon of cyclopropanol and N5 of flavin. Methanol oxidase was also reconstituted with 5-deazaflavin adenine dinucleotide (dFAD). Reconstituted enzyme did not catalyze the oxidation of alcohols to the corresponding aldehydes, nor did reduced reconstituted enzyme catalyze the reverse reaction. Incubation of reconstituted enzyme with cyclopropanol resulted in an absorbance decrease at 399 nm, but no irreversible covalent modification of the deazaflavin cofactor. A reversible addition complex between cyclopropanol and dFAD is formed. The structure of that complex was not definitively established, but it is likely that it is formed through the addition of cyclopropoxide to C5 of dFAD. The failure of dFAD-reconstituted methanol oxidase to catalyze the oxidation of substrate, as well as the lack of reaction with cyclopropanol, supports a radical mechanism for alcohol oxidation and cyclopropanol inactivation. Methanol oxidase catalyzes the oxidation of cyclopropylcarbinol to the corresponding aldehyde. No ring-opened products were detected. The failure to form ring-opened products has been used as an argument against radical processes [MacInnes, I., Nonhebel, D. C., Orsculik, S. T., & Suckling, C. J. (1982) J. Chem. Soc., Chem. Commun., 121-122]. We present arguments against this interpretation.

Alcohol Oxidoreductases↗
PubMed1999

Structure of the flavocoenzyme of two homologous amine oxidases: monomeric sarcosine oxidase and N-methyltryptophan oxidase.

Monomeric sarcosine oxidase (MSOX) and N-methyltryptophan oxidase (MTOX) are homologous enzymes that catalyze the oxidative demethylation of sarcosine (N-methylglycine) and N-methyl-L-tryptophan, respectively. MSOX is induced in various bacteria upon growth on sarcosine. MTOX is an E. coli enzyme of unknown metabolic function. Both enzymes contain covalently bound flavin. The covalent flavin is at the FAD level as judged by electrospray mass spectrometry. The data provide the first evidence that MTOX is a flavoprotein. The following observations indicate that 8alpha-(S-cysteinyl)FAD is the covalent flavin in MSOX from Bacillus sp. B-0618 and MTOX. FMN-containing peptides, prepared by digestion of MSOX or MTOX with trypsin, chymotrypsin, and phosphodiesterase, exhibited absorption and fluorescence properties characteristic of an 8alpha-(S-cysteinyl)flavin and could be bound to apo-flavodoxin. The thioether link in the FMN-containing peptides was converted to the sulfone by performic acid oxidation, as judged by characteristic absorbance changes and an increase in flavin fluorescence. The sulfone underwent a predicted reductive cleavage reaction upon treatment with dithionite, releasing unmodified FMN. Cys315 was identified as the covalent FAD attachment site in MSOX from B. sp. B-0618, as judged by the sequence obtained for a flavin-containing tryptic peptide (GAVCMYT). Cys315 aligns with a conserved cysteine in MSOX from other bacteria, MTOX (Cys308) and pipecolate oxidase, a homologous mammalian enzyme known to contain covalently bound flavin. There is only one conserved cysteine found among these enzymes, suggesting that Cys308 is the covalent flavin attachment site in MTOX.

Amino Acid Sequence↗
PubMed1986

Studies of monoamine oxidase and semicarbazide-sensitive amine oxidase. I. Inhibition by a selective monoamine oxidase-B inhibitor, MD 780236.

In vitro studies of the effect of MD 780236, a selective monoamine oxidase (MAO)-B inhibitor, on a semicarbazide-sensitive amine oxidase (SSAO) in rat testis and lung showed that this compound dose-dependently inhibited SSAO activity. The extents of inhibition of MAO-A, -B and SSAO in these two rat tissues by this compound after 30 min of preincubation were found to be MAO-B greater than MAO-A greater than SSAO. This selectivity was also evident in preparations without preincubation. Degree of inhibition of SSAO was not significantly influenced by pretreatment with either 10(-3) M clorgyline, I-deprenyl or 10(-4) M SKF 525A. Inhibition of SSAO was not enhanced by varying the time of preincubation of the enzyme and the compound, indicating direct action on and reversible inhibition of SSAO. The inhibition of SSAO by MD 780236 was non-competitive with or without preincubation, with a K1 value of 110 muM. Although MD 780236 is a selective and "suicide substrate" inhibitor of MAO-B, these present results indicate that this compound may also inhibit SSAO activity, but by a mechanism different from that for MAO-B. These findings confirm an earlier hypothesis that compounds that inhibit both MAO and SSAO have totally different modes of action on these two different amine oxidases.

Animals↗
PubMed1986

Inhibition of monoamine oxidase A-form and semicarbazide-sensitive amine oxidase by selective and reversible monoamine oxidase-A inhibitors, amiflamine and FLA 788(+).

In vitro studies demonstrated that two selective monoamine oxidase (MAO)-A inhibitors, amiflamine and FLA 788(+), have been shown to inhibit semicarbazide-sensitive amine oxidase (SSAO) in rat testis and lung homogenates in a concentration-dependent way. The inhibition was not greatly influenced by pretreatment of the preparations with either clorgyline (10(-3) mol/l), l-deprenyl (10(-3) mol/l) or SKF 525A (10(-4) mol/l). The two compounds showed a time-dependent inhibition of SSAO, and for the initial phase of the inhibition, amiflamine is a competitive inhibitor with a Kislope of 135 mumol/l, but FLA 788(+) is a noncompetitive inhibitor with a Ki value of 180 mumol/l. After preincubation for 60 min at 37 degrees C, however, inhibition by amiflamine was found to be essentially irreversible whereas that produced by FLA 788(+) was still noncompetitive and reversible. These two compounds also reversibly and competitively inhibited rat testis MAO-A with FLA 788(+) being much more selective towards this MAO (Kislope = 0.26 mumol/l for FLA 788(+) and 7 mumol/l for amiflamine, respectively). The present results indicate that both MAO-A-selective inhibitors also inhibit SSAO in vitro, but their properties as SSAO inhibitors differ from those as MAO-A inhibitors.

Animals↗
PubMed1979

Semiconduction as the mechanism of the cytochrome oxidase reaction. Low activation energy of semiconduction measured for cytochrome oxidase protein. Solid state theory of cytochrome oxidase predicts observed kinetic peculiarities.

Cytochrome oxidase protein has a measured activation energy of semiconduction much smaller than that of other proteins, falling within the range of the activation energy of the cytochrome oxidase reaction in solution. Many kinetic peculiarities of the cytochrome oxidase reaction difficult to explain by mass-action theories are easily accounted for if semiconduction is assumed to be the controlling mechanism.

Catalysis↗
PubMed1998

Rat D-amino-acid oxidase cDNA: rat D-amino-acid oxidase as an intermediate form between mouse and other mammalian D-amino-acid oxidases.

Nucleotide sequence of cDNA encoding rat D-amino-acid oxidase (DAO) was determined. Two species of DAO mRNA were present in rat kidney, liver, and brain. They were probably produced by alternative splicing. Rat DAO cDNA encodes 346 amino acid residues, indicating that rat DAO is an intermediate form between mouse DAO (345 amino acids) and DAOs (347 amino acids) of human, rabbit, and pig. Deduced amino acid sequence indicates 93% identity between rat and mouse DAO. Northern hybridization and western blotting supported the sequence data.

Amino Acid Sequence↗
PubMed1976

Oxidation of selected pteridine derivatives by mamalian liver xanthine oxidase and aldehyde oxidase.

Considerable information is available concerning the oxidation of pteridine derivatives by bovine milk xanthine oxidase, but few investigations have been carried out on the oxidation of such compounds by mammalian liver xanthine oxidase and the related aldehyde oxidase. Xanthine oxidase, obtained from rat liver, oxidizes a variety of substituted amino- and hydroxypteridines in a manner identical to that previously observed for milk xanthine oxidase. For example, 2-aminopteridine and its 4- and 7-hydroxy derivatives were oxidized efficiently to 2-amino-4,7-dihydroxypteridine (isoxanthopterin) by the rat liver enzyme, and 4-aminopteridine and its 2- and 7-hydroxy derivatives were oxidized to 4-amino-2,7-dihydroxypteridine.4-Hydroxypteridine and the isomeric 2- and 7-hydroxypteridines were oxidized by rat liver xanthine oxidase to 2,4,7-trihydroxypteridine. Rabbit liver aldehyde oxidase, but not rat liver xanthine oxidase, was able to catalyze the oxidation in position 7 of 2,4-diaminopteridine and its 6-methyl and 6-hydroxymethyl derivatives. 2-Aminopteridine and 4-aminopteridine were both oxidized to the corresponding 7-hydroxy derivatives in the aldehyde oxidase system; 2-amino-4-hydroxypteridine appeared to be a minor product in the oxidation of 2-aminopteridine by rabbit liver aldehyde oxidase. Both aldehyde oxidase and xanthine oxidase were able to catalyze the oxidation of 2-amino-6,7-disubstituted pteridines to the corresponding 4-hydroxy derivatives; 4-hydroxy-6,7-disubstituted pteridines were oxidized in position 2 by both enzymes. 4-Amino-6,7-disubstituted pteridines were not oxidized by either enzyme. 2-Amino-4-methylpteridine was oxidized in position 7 by aldehyde oxidase but was not an effective substrate for xanthine oxidase; 2-hydroxypteridine and 7-hydroxypteridine were not oxidized to a detectably extent by aldehyde oxidase. All oxidations mediated by xanthine oxidase were strongly inhibited by allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine), and all oxidations mediated by aldehyde oxidase were inhibited by menadione (2-methyl-1,4-naphthoquinone). Rat liver xanthine oxidase and, to a lesser extent, rabbit liver aldehyde oxidase were inhibited by 4-chloro-6,7-dimethylpteridine; 2-amino-3-pyrazinecarboxylic acid inhibited xanthine oxidase but not aldehyde oxidase. The oxidations of 2- and 4-aminopteridines by aldehyde oxidase resulted in concomitant reduction of cytochrome c.

Aldehyde Oxidoreductases↗