Behavioural and electrocortical effects after injection of two ornithine decarboxylase inhibitors into several areas of the brain in the rat

The behavioural and electrocortical effects of alpha-methylornithine and alpha-difluoromethylornithine, two ornithine decarboxylase inhibitors, were evaluated after their infusion into several areas of the brain in the rat. Both compounds induced, in dose-dependent manner, similar epileptogenic effects, stereotyped behaviour and postural asymmetry, depending upon the site of injection. Unilateral injection of DFMO into the entopeduncular nucleus or the substantia nigra pars reticulata, caused an increase in locomotor activity. Unilateral injection of DFMO into the caudate nucleus or the substantia nigra pars compacta had no effect on locomotor activity. Among the areas of the brain studied, the most sensitive site from which electrocortical epileptogenic disorders were evoked, was the hippocampus. The GABA agonist muscimol, infused prior to DFMO, resulted in an anticonvulsant action, while DFMO, infused prior to putrescine, increased the convulsant properties of putrescine. In conclusion, these results indicate that DFMO and alpha-methylornithine produced epileptogenic effects after their intracerebral infusion and suggest that may act as analogues of putrescine.

Arginine restriction induced by delta-N-(phosphonacetyl)-L-ornithine signals increased expression of HIS3, TRP5, CPA1, and CPA2 in Saccharomyces cerevisiae

delta-N-(Phosphonacetyl)-L-ornithine (PALO), a transition state analog inhibitor of ornithine transcarbamylase, induced arginine limitation in vivo in Saccharomyces cerevisiae. Arginine restriction caused increased expression of HIS3 and TRP5, measured by the beta-galactosidase activity in strains carrying chromosomally integrated fusions of the promoter regions of each gene with the lacZ gene of Escherichia coli. The increase in beta-galactosidase activity induced by PALO was reversed by the addition of arginine and was dependent on GCN4 protein. These results indicate that PALO, like 3-amino-1,2,4-triazole DL-5-methyltryptophan, can be used to study the effect of limitation of a single amino acid, arginine, on the expression of genes under the general amino acid control regulatory system. Arginine deprivation imposed by PALO also caused increased expression of CPA1 and CPA2, coding respectively for the small and large subunits of arginine-specific carbamyl-phosphate synthetase. The observed increase was GCN4 dependent and was genetically separable from arginine-specific repression of CPA1 mRNA translation. The 5'-flanking regions of CPA1 (reported previously) and CPA2 determined in this study each contained at least two copies of the sequence TGACTC, shown to bind GCN4 protein. The beta-galactosidase activities expressed from CPA1- and CPA2-lacZ fusions integrated into the nuclear DNA of gcn4 mutant strains were five to six times less than in the wild type, when both strains were grown under depressed conditions. The gcn4 mutation reduced basal expression of both CPA1 and CPA2. The addition of arginine to strains containing the CPA1-lacZ fusion further reduced beta-galactosidase activity of the gcn4 mutant, indicating independent regulation of the CPA1 gene by the general amino acid control and by arginine-specific repression. In strains overproducing GCN4 protein, the translational control completely overrode transcriptional activation of CPA1 by general amino acid control.

Stimulus-secretion coupling of arginine-induced insulin release. Metabolism of L-arginine and L-ornithine in pancreatic islets

Exogenous L-arginine and L-ornithine rapidly accumulate in rat pancreatic islets. L-Arginine is converted to L-ornithine and urea. Endogenous or exogenous L-ornithine generates di- and polyamines, the putrescine turnover being faster than that of spermidine and spermine. However, the major pathway for L-ornithine metabolism consists of its transamination to L-glutamaldehyde and further conversion to L-glutamate. The amines and L-glutamate derived from exogenous L-ornithine are incorporated into islet proteins at the intervention of transglutaminase and cycloheximide-sensitive biosynthetic processes, respectively. These findings suggest the hypothesis that the insulinotropic action of L-arginine and L-ornithine could somehow be related to the metabolism of these cationic amino acids in islet cells.

Glutamine and ornithine-alpha-ketoglutarate but not branched-chain amino acids reduce the loss of muscle glutamine after surgical trauma

The concentration of free glutamine in skeletal muscle decreases characteristically after surgical trauma. In animal studies a correlation between muscle protein synthesis and the glutamine concentration is reported. For pharmaceutical reasons, commercially available amino acid solutions do not contain glutamine. Therefore, at present, postoperative total parenteral nutrition does not provide glutamine. Several modifications of the composition of the amino acid solutions given in total parenteral nutrition have been evaluated recently. Ornithine-alpha-ketoglutarate preserves muscle protein synthesis and spares nitrogen after elective surgery, and an extra supply of branched-chain amino acids improves muscle protein synthesis in animals. Patients undergoing elective abdominal surgery (n = 33) received isocaloric (135 kJ/kg body weight/24 h) and isonitrogenous (0.2 g N/kg body weight/24 h) total parenteral nutrition for three days immediately following surgery. Administration of glutamine and ornithine-alpha-ketoglutarate as part of the amino acid supply reduced the loss of muscle glutamine from 40% to 25% (P less than .05). Additional supplementation of branched-chain amino acids produced no such effect, however, as compared with the control group. Further clinical trials including glutamine and ornithine-alpha-ketoglutarate are advocated.

Macrophage activation by an ornithine-containing lipid or a serine-containing lipid

alpha-N-(3-Acyloxyacyl)-ornithine (or -serine) is the structure of lipoamino acids obtained by us previously from some gram-negative bacteria (Y. Kawai and I. Yano, Eur. J. Biochem. 136:531-538, 1983; Y. Kawai, I. Yano, and K. Kaneda, Eur. J. Biochem. 171:73-80, 1988; Y. Kawai, I. Yano, K. Kaneda, and E. Yabuuchi, Eur. J. Biochem. 175:633-641, 1988). The 3-acyloxyacylamide structure is present in both the lipoamino acids and lipid A of lipopolysaccharide (endotoxin). The efficacy of lipoamino acids (an ornithine-containing lipid and a serine-containing lipid) in activating C3H/HeSlc mouse peritoneal exudate macrophages was compared with that of bacterial lipopolysaccharide, because the two types of substances were expected to exhibit similar biological activities and physiological functions on the basis of their structural similarities. Actually, the lipoamino acids, as well as lipopolysaccharide, strongly activated the macrophages to generate the immunoregulatory substances prostaglandin E2 and interleukin-1, but their effect on the induction of L929 cell cytolytic factor (a possible tumor necrosis factor), another immunoregulatory substance, was weaker than that of lipopolysaccharide. The effect of lipoamino acids on the cytotoxicity of macrophages for EL-4 leukemia cells was very weak. However, all of these activities, as far as tested, were strongly enhanced by synergistic action with gamma interferon. Only the serine-containing lipid killed both C3H/HeSlc and C3H/HeJ macrophages to almost the same degree as endotoxin killed C3H/HeSlc macrophages. On the other hand, lethal toxicity for mice was not found with either the ornithine-containing lipid or the serine-containing lipid, even when 7 mg of compound was injected into a mouse. These studies suggest that the lipoamino acids are nontoxic characteristic immunoactivators.

N5-(L-1-carboxyethyl)-L-ornithine:NADP+ oxidoreductase from Streptococcus lactis. Purification and partial characterization

N5-(L-1-Carboxyethyl)-L-ornithine:NADP+ oxidoreductase (EC 1.5.1.-) from Streptococcus lactis K1 has been purified 8,000-fold to homogeneity. The NADPH-dependent enzyme mediates the reductive condensation between pyruvic acid and the delta- or epsilon-amino groups of L-ornithine and L-lysine to form N5-(L-1-carboxyethyl)-L-ornithine and N6-(L-1-carboxyethyl)-L-lysine, respectively. The five-step purification procedure involves ion-exchange (DE52 and phosphocellulose P-11), gel filtration (Ultrogel AcA 44), and affinity chromatography (2',5'-ADP-Sepharose 4B). Approximately 100-200 micrograms of purified enzyme of specific activity 40 units/mg were obtained from 60 g of cells, wet weight. Anionic polyacrylamide gel electrophoresis revealed a single enzymatically active protein band, whereas three species (pI 4.8-5.1) were detected by analytical electrofocusing. The purified enzyme is active over a broad pH range of 6.5-9.0 and is stable to heating at 50 degrees C for 10 min. Substrate Km values were determined to be: NADPH, 6.6 microM; pyruvate, 150 microM; ornithine, 3.3 mM; and lysine, 18.2 mM. The oxidoreductase has a relative molecular mass (Mr = 150,000) as estimated by high pressure liquid chromatography exclusion chromatography and by polyacrylamide gradient gel electrophoresis. Conventional gel filtration indicated an Mr = 78,000, and a single protein band of Mr = 38,000 was revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is composed of identical subunits of Mr = 38,000, which may associate to yield both dimeric and tetrameric forms. Polyclonal antibody to the purified protein inhibited enzyme activity. The amino acid composition of the enzyme is reported, and the sequence of the first 37 amino acids from the NH2 terminus has been determined by stepwise Edman degradation.

(6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydrofolate and 6(R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-ornithine as potential antifolates and antitumor agents

(6R,6S)-5,8,10-Trideaza-5,6,7,8-tetrahydropteroic acid was synthesized in several steps from 4,4-(ethylenedioxy)-cyclohexanone and [4-(tert-butyloxycarbonyl)benzyl]triphenylphosphonium bromide and was elaborated to (6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-glutamic acid and (6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-ornithin e. Compound 1 was found to be a good substrate for partially purified mouse liver folypolyglutamate synthetase (FPGS), with a Michaelis constant (Km = 15 microM) comparable to that reported for the reduced folate substrate (6S)-5,6,7,8-tetrahydropteroyl-L-glutamic acid and for (6R,6S)-5,10-dideaza-5,6,7,8-tetrahydropteroyl-L-glutamic acid (DDATHF). However, in striking contrast to DDATHF, which is potently cytotoxic, 1 failed to inhibit tumor cell growth in culture at concentrations of up to 100 microM. These results suggested that the NH at position 8 of DDATHF is important for cytotoxic activity but not for polyglutamylation. Just as 1 was a good substrate for FPGS, the ornithine analogue 2 proved to be among the more potent competitive inhibitors of this enzyme discovered to date, with a Ki,s of 10 microM. While the binding affinity of 2 was lower than that reported for 5,6,7,8-tetrahydropteroyl-L-ornithine (H4PteOrn), very substantial FPGS inhibition was observed even though N5,N8, and N10 in H4PteOrn were replaced by carbon. Binding to FPGS thus appears to be tolerant of bioisosteric replacements made simultaneously in ring B and the bridge region. Neither 1 nor 2 was active in preventing cell growth in culture at concentrations of up 100 microM. The N delta-hemiphthaloyl derivative of 2, synthesized as a potential prodrug, was also inactive.

Ornithine aminotransferase activity, tissue ornithine concentrations and polyamine metabolism

1. Inactivation of L-ornithine:2-oxoacid aminotransferase (OAT) by 5-fluoromethylornithine (5FMOrn), a specific inactivator of OAT, causes a great elevation of tissue ornithine (Orn) concentrations. 2. Inhibition of L-ornithine decarboxylase (ODC) by 2-difluoromethylornithine (DFMO) had no effect on Orn concentrations. 3. The combined administration of 5FMOrn and DFMO produced a 2- to 3-fold greater enhancement of tissue Orn concentrations than treatment with 5FMOrn alone. 4. The increase of tissue Orn concentrations had a long-lasting enhancing effect on polyamine metabolism. 5. In the brain this could be demonstrated by the elevation of putrescine and spermidine concentrations and the increase of spermidine turnover rate. 6. In visceral organs polyamine concentrations were not elevated because polyamines can be eliminated by transport. 7. In line with this notion is the fact that urinary polyamine excretion was increased for several days, even after a single dose of 5FMOrn. 8. Inhibitors of 4-aminobutyric acid:2-oxoglutarate aminotransferase which are also inactivators of OAT had the same effect on polyamine excretion as 5FMOrn.

Inhibition of ornithine carbamoyltransferase from Pseudomonas syringae pv. syringae W50 by phaseolotoxin

In contrast to the producer of phaseolotoxin and Orn-P(O)(NH2)-NH-SO3H (PNSOrn), Pseudomonas syringae pv. phaseolicola, which possesses a sensitive and an insensitive type of ornithine carbamoyltransferase (OCT, E.C. 2.1.3.3.), in Pseudomonas syringae pv. syringae W50, an organism which produce neither phaseolotoxin nor PNSOrn, only one type of OCT could be detected. This enzyme is highly sensitive to phaseolotoxin. This result supports our hypothesis that the existence of an insensitive ornithine carbamoyltransferase is an important prerequisite for the synthesis of phaseolotoxin in P. syringae pv. phaseolicola and that this enzyme does not occur generally in P. syringae spec.

Modulation of albumin secretion by ornithine alpha-ketoglutarate in adult rat hepatocyte cultures and a human hepatoma cell line (HepG2)

Cocultured adult rat hepatocytes and a human hepatoma cell line (HepG2) were maintained in an arginine-free medium with or without ornithine alpha-ketoglutarate. This drug increased greatly hepatocyte albumin secretion in both culture models. L-Ornithine was the component accounting for these effects since similar data were obtained by using this sole amino acid. Moreover, we observed that L-ornithine stimulation of albumin production was via polyamine synthesis. Since a correlated increase in albumin mRNA was observed, it may be postulated that ornithine alpha-ketoglutarate acts at a pretranslational level.

Detection of an insensitive ornithine-carbamoyltransferase in strains of Pseudomonas syringae pv. phaseolicola with different phytotoxin-generating capacities

Independently of their capacity to produce phytotoxins, strains of Pseudomonas syringae pv. phaseolicola contain two ornithine carbamoyltransferases (OCT, EC 2.1.3.3) which differ in resistance to phaseolotoxin and Orn-P(O) (NH2)-NH-SO3 H (PNSOrn). At 18 degrees C, the optimal temperature for product formation, the balance of the two types of OCT was shifted in favour of the insensitive type in phaseolotoxin producing strains, and in favour of the sensitive one in strains with little or no toxin production. The results suggest a causal relationship between the existence of an insensitive enzyme and the synthesis of toxins.

Inhibition of porphyrin biosynthesis by exogenous 5-aminolevulinic acid in an aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

Exogenously administered 5-aminolevulinic acid (ALA) inhibited the formation of bacteriochlorophyll a (Bchl a) in a dose-dependent manner in the aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114, under dark growth conditions. The ALA concentration required for half-inhibition after 24-h growth was estimated to be about 3.0 mM. Porphyrin and Bchl precursors were not found in either the cells or the growth medium. The same inhibition was also observed with cytochrome c formation. When ALA was incubated with intact cells, a large amount of ALA was converted to an unknown metabolite. The pH optimum of the conversion was 7.8. The metabolite did not react with Ehrlich's reagent, but did so with ninhydrin, giving a yellow color. Based on analyses by several techniques including mass spectrometry, ir spectrometry, and paper electrophoresis, it was identified as 4-hydroxy-5-aminovaleric acid (HAVA). Authentic HAVA prepared from ALA was a competitive inhibitor of the enzyme, porphobilinogen synthase of Erythrobacter. The Ki value for authentic HAVA was calculated to be 2.4 mM from a Dixon plot and the HAVA concentration required for half-inhibition was 17 mM. It is concluded that in Erythrobacter cells, exogenous ALA is converted to the metabolite, HAVA, which is responsible for the inhibition of porphobilinogen synthase as well as that of Bchl a and cytochrome formation.

O-dephenylation and conjugation with benzoylornithine. New metabolic pathways for 3-phenoxybenzoic acid in chickens

Metabolism of [benzyl-14C]fluvalinate by chickens produces 3-phenoxybenzoic acid, which is further degraded by two new pathways. The first pathway involves O-dephenylation, not reported previously for related pyrethroids in birds or mammals. O-Dephenylation is a major metabolic route (12% of the applied 14C). In the second pathway, 2% of the applied dose is converted into four conjugates of benzoylornithine (two with 3-hydroxybenzoic and two with 3-phenoxybenzoic acids). The predominant conjugate with benzoylornithine is N2-(3-hydroxybenzoyl)-N5-benzoylornithine.

Structural specificity of inhibition of human folylpolyglutamate synthetase by ornithine-containing folate analogs

A series of folate analogs containing ornithine instead of glutamate was synthesized and tested for inhibition of folylpolyglutamate synthetase (FPGS) and other folate-dependent enzymes of human leukemia cell lines. Reduced derivatives of 2-amino-4-oxo-10-methyl-pteroyl-ornithine had dramatically increased inhibitory potency against FPGS compared to the oxidized parent. The amino-pterin analog (2,4-diamino-pteroylornithine) was a potent inhibitor of both dihydrofolate reductase and FPGS. It was a much more potent linear competitive inhibitor of human FPGS than the corresponding methotrexate derivative previously described (Ki = 0.15-0.26 and 3 microM respectively). A quinazoline folate analog, 2-amino-4-oxo-5,8-dideazapteroyl-ornithine, was a relatively poor inhibitor of isolated dihydrofolate reductase and thymidylate synthase; however, it is the most potent human FPGS inhibitor identified to date (Ki = 100-150 nM). Because of the lack of appreciable interaction with other folate-dependent enzymes, structures incorporating the 2-amino-4-oxo-5,8-dideazapteroate nucleus may thus lead to selective inhibition of FPGS. Substitution of ornithine for glutamate caused a profound decrease in cytotoxic potency for these analogs; this was apparently the result of poor transport. Together with earlier studies, these data indicate that the potency of FPGS inhibition by an analog containing ornithine closely parallels the relative substrate activity of its glutamate-containing counterpart. The substitution of ornithine apparently does not perturb the pterin specificity of FPGS. The close parallel between substrate and inhibitor specificity may thus allow the use of currently available structure-activity studies on FPGS to design more potent and more selective inhibitors of FPGS.

N2-succinylornithine in ornithine catabolism of Pseudomonas aeruginosa

Most Pseudomonas aeruginosa PAO mutants which were unable to utilize L-arginine as the sole carbon and nitrogen source (aru mutants) under aerobic conditions were also affected in L-ornithine utilization. These aru mutants were impaired in one or several enzymes involved in the conversion of N2-succinylornithine to glutamate and succinate, indicating that the latter steps of the arginine succinyltransferase pathway can be used for ornithine catabolism. Addition of aminooxyacetate, an inhibitor of the N2-succinylornithine 5-aminotransferase, to resting cells of P. aeruginosa in ornithine medium led to the accumulation of N2-succinylornithine. In crude extracts of P. aeruginosa an ornithine succinyltransferase (L-ornithine:succinyl-CoA N2-succinyltransferase) activity could be detected. An aru mutant having reduced arginine succinyltransferase activity also had correspondingly low levels of ornithine succinyltransferase. Thus, in P. aeruginosa, these two activities might be due to the same enzyme, which initiates aerobic arginine and ornithine catabolism.

5-Fluoromethylornithine, an irreversible and specific inhibitor of L-ornithine:2-oxo-acid aminotransferase

5-Fluoromethylornithine (5-FMOrn) is the first specific irreversible inhibitor of L-ornithine:2-oxoacid aminotransferase (OAT) found. Single doses (greater than 10 mg/kg) of this compound inactivate OAT to a residual OAT-like activity. This activity (10-20% of total activity) is resistant to further inactivation by higher or repeated doses of 5-FMOrn, or incubation with the inactivator in vitro. Ornithine concentrations are greatly enhanced in various tissues, and urinary ornithine is dramatically increased, but no other amino acid is affected after acute treatment with 5-FMOrn. Repeated administration decreases carnosine and homocarnosine concentrations in brain. Toxic effects were not observed. The new inactivator is considered as a tool in the establishment of functions of OAT under physiological and pathological conditions.

Methotrexate analogues. 33. N delta-acyl-N alpha-(4-amino-4-deoxypteroyl)-L-ornithine derivatives: synthesis and in vitro antitumor activity

N delta-Acyl derivatives of the potent folylpolyglutamate synthetase (FPGS) inhibitor N alpha-(4-amino-4-deoxypteroyl)-L-ornithine (APA-L-Orn) were synthesized from N alpha-(4-amino-4-deoxy-N10-formylpteroyl)-L-ornithine by reaction with an N-(acyloxy)succinimide or acyl anhydride, followed by deformylation with base. The N delta-hemiphthaloyl derivative was also prepared from 4-amino-4-deoxy-N10-formylpteroic acid by reaction with persilylated N delta-phthaloyl-L-ornithine, followed by simultaneous deformylation and ring opening of the N delta-phthaloyl moiety with base. The products were potent inhibitors of purified dihydrofolate reductase (DHFR) from L1210 murine leukemia cells, with IC50's ranging from 0.027 and 0.052 microM as compared with 0.072 microM for APA-L-Orn. Several of the N delta-acyl-N10-formyl intermediates also proved to be good DHFR inhibitors. One of them, N alpha-(4-amino-4-deoxy-N10-formylpteroyl)-N delta-(4-chlorobenzoyl)-L- ornithine, had a 2-fold lower IC50 than its deformylated product, confirming that the N10-formyl group is well tolerated for DHFR binding. While N delta-acylation of APA-L-Orn did not significantly alter anti-DHFR activity, inhibition of FPGS was dramatically diminished, supporting the view that the basic NH2 on the end of the APA-L-Orn side chain is essential for the activity of this compound against FPGS. N delta-Acylation of APA-L-Orn markedly enhanced toxicity to cultured tumor cells. However, N delta-acyl derivatives also containing an N10-formyl substituent were less cytotoxic than the corresponding N10-unsubstituted analogues even though their anti-DHFR activity was the same, suggesting that N10-formylation may be unfavorable for transport. Two compounds, the N delta-benzoyl and N delta-hemiphthaloyl derivatives of APA-L-Orn, with IC50's against L1210 cells of 0.89 and 0.75 nM, respectively, were more potent than either methotrexate (MTX) or aminopterin (AMT) in this system. These compounds were also more potent than MTX against CEM human lymphoblasts and two human head and neck squamous cell carcinoma cell lines (SCC15, SCC25) in culture. Moreover, in assays against SCC15/R1 and SCC25/R1 sublines with 10-20-fold MTX resistance, the N delta-hemiphthaloyl derivative of APA-L-Orn showed potency exceeding that of MTX itself against the parental cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Biosynthesis and stereochemical configuration of N5-(1-carboxyethyl)ornithine. An unusual amino acid produced by Streptococcus lactis

In a recent communication (Thompson, J., Curtis, M. A., and Miller, S.P.F. (1986) J. Bacteriol. 167, 522-529) we described the purification and characterization of N5-(1-carboxyethyl)ornithine from cells of Streptococcus lactis 133. This unusual amino acid has not previously been found in nature. Radiotracer experiments presented here reveal that exogenous [14C]ornithine serves as the precursor for biosynthesis of [14C]arginine, [14C]N5-(1-carboxyethyl)ornithine, and [14C]N5-acetylornithine by cells of S. lactis K1 during growth in a defined medium lacking arginine. In the absence of both arginine and ornithine, cells of S. lactis K1 can also generate intracellular [14C]N5-(1-carboxyethyl)ornithine from exogenous [14C]glutamic acid. Previously we showed that the properties of N5-(1-carboxyethyl)ornithine prepared from S. lactis were identical to one of the two diastereomers [2S, 7S) or (2S, 7R] present in a synthetic preparation of (2S, 7RS)-N5-(1-carboxyethyl)ornithine. The two diastereomers have now been unambiguously synthesized by an Abderhalden-Haase condensation between (2S)-N2-t-butoxycarbonyl-ornithine and the chiral (2S)-, and (2R)-bromopropionates. By 13C-NMR spectroscopy it has been established that the preparation from S. lactis is exclusively (2S, 7S)-N5-(1-carboxyethyl)ornithine. has been demonstrated in a cell-free extract of S. lactis 133. The requirements for ornithine, pyruvic acid, and NAD(P)H suggest that biosynthesis of N5-(1-carboxyethyl)ornithine occurs via a reductive condensation mechanism. A general survey revealed that N5-(1-carboxyethyl)ornithine was produced only by certain strains of Group N streptococci. These findings may indicate a plasmid locus for the gene(s) encoding the enzyme(s) for N5-(1-carboxyethyl)ornithine biosynthesis.

Ornithine-alpha-ketoglutarate improves skeletal muscle protein synthesis as assessed by ribosome analysis and nitrogen use after surgery

Total parenteral nutrition (TPN) was given for 3 days after elective abdominal surgery. The control group (N = 9) received TPN only and one group of patients (N = 6) received TPN supplemented with ornithine-alpha-ketoglutarate (0.35 g/kg bw/day). Protein synthesis in skeletal muscle was assessed from the total ribosome concentration and the percentage of polyribosomes. In the control group the total concentration of ribosomes decreased after surgery by 23% (p less than 0.05) and the percentage of polyribosomes decreased by 21% (p less than 0.01), whereas in the ornithine-alpha-ketoglutarate group both variables remained unaffected. The cumulative urinary urea excretion was significantly larger in the control group than in the ornithine-alpha-ketoglutarate group (p less than 0.05). The calculated nitrogen balance was negative in the control group on each day of the study (p less than 0.05), but that of the ornithine-alpha-ketoglutarate group was not statistically different from zero. The results show that postoperative maintenance of muscle protein synthesis and a more effective nitrogen use was achieved by supplementing TPN with ornithine-alpha-ketoglutarate, 0.35 g/kg bw/day.

Influence of enterally administered ornithine alpha-ketoglutarate on hormonal patterns in burn patients

Plasma concentrations of glucose, insulin, C-peptide, glucagon, cortisol and hGH were measured in burn patients (mean burn surface area 21 per cent) treated or not with ornithine alpha-ketoglutarate (OKG). An increase in basal values of glucose, insulin, C-peptide and cortisol was demonstrated in both groups, whereas hGH values diminished. OKG modified neither insulin nor hGH values 24 h after its enteral administration nor insulin levels within the first 4 h after intake. On the other hand, 60 min after enteral nutrition was restarted the hyperglycaemia observed in untreated subjects was reduced by OKG whereas a hyperinsulinism was observed in both groups. These results suggest that: (i) the anticatabolic/anabolic action of OKG in burn patients is not mediated by insulin or hGH, (ii) OKG probably induces an increase in glucose tolerance in burn patients, in whom there is a state of insulin resistance. The mechanism of this action requires further study.

Resolution of the enantiomers of various alpha-substituted ornithine and lysine analogs by high-performance liquid chromatography with chiral eluant and by gas chromatography on Chirasil-Val

A reversed-phase high-performance liquid chromatography method, with L-proline and copper as chiral mobile phase, is described for the enantiomeric resolution of various alpha-substituted ornithine and lysine analogs. Although ornithine gives no separation with the chiral eluant used, excellent resolutions are obtained for various alpha-alkyl-, alpha-halogenomethyl-, alpha-vinyl-, and alpha-ethynyl-substituted ornithines. Similar separations are also observed for the dehydroornithine and lysine analogs. Gas chromatography on a chiral stationary phase, Chirasil-Val, allows the resolution of the ornithine and lysine analogs after derivatization into the monofluoroacyl derivatives of their corresponding lactams. No resolution or only a poor resolution is obtained by GC on Chirasil-Val for the dehydroornithine analogs as their di-N-perfluoroacyl alkyl esters. The chiral eluant HPLC procedure is easily scaled up for the semipreparative resolution of several ornithine analogs, i.e., alpha-fluoromethylornithine, alpha-difluoromethylornithine, alpha-chlorofluoromethylornithine, and alpha-fluoromethyldehydroornithine, which are known as potent ornithine decarboxylase inhibitors in vitro and in vivo.

Characterization of two ornithine carbamoyltransferases from Pseudomonas syringae pv. phaseolicola, the producer of phaseolotoxin

Two ornithine carbamoyltransferases (OCT 1 and OCT 2) were isolated from Pseudomonas syringae pv. phaseolicola and purified by precipitation with ammonium sulfate, heat denaturation, chromatography on DEAE-Sephadex A-50 and Sephadex G-200. Molecular weights of both enzymes: 110,000; optimal activity: pH 8.5 to 9.5 (OCT 1), pH 8.4 (OCT 2); apparent Km for ornithine: 7 X 10(-4) (both enzymes); apparent Km for carbamoyl-phosphate: 7 X 10(-4) (OCT 1), 2.8 X 10(-3) (OCT 2). Both enzymes possess only an anabolic function. OCT 1 is highly inhibited by low concentrations of phaseolotoxin and Orn-P(O)(NH2)-NH-SO3H, OCT 2 is insensitive to both compounds. The inhibition of OCT 1 is reversible.

Occurrence, identification and possible significance of ornithine lipid in Thiobacillus ferrooxidans

An ornithine containing aminolipid has been found in Thiobacillus ferrooxidans grown in ferrous sulfate medium, which was purified and estimated at four main phases of growth. GLC analysis of ornithine lipid has revealed the existence of mainly C18:1 and C22:1 fatty acids. The infrared spectra showed the existence of both amide and ester linkages in the aminolipid. The major ester linked fatty acid was C22:1. The interaction of ornithine lipid with membrane was investigated by delipidation of the membrane particles, which resulted in the perturbation of the activities of the three enzymes of iron oxidation system. The activities could be restored to the lipid depleted particles by preincubation with a dispersion of purified ornithine lipid together with coenzyme Q8. The kinetic parameters of the enzyme activities were also affected by delipidation which was significantly altered in the reconstituted particles by this lipid, thus indicating a possible role of ornithine lipid in iron oxidation system.