Arginase as a useful factor for the diagnosis of colorectal cancer liver metastases.

The present work is a continuation of studies on arginase as a marker in the diagnosis of colorectal cancer liver metastases (CRCLM). The purpose of the study was the evaluation of the arginase test in comparison with other colorectal cancer tests such as CEA, CA 19-9 and biochemical markers of liver function such as aspartate aminotransferase (AST) and alanine aminotransferase (ALT). The studies were conducted on blood serum from 85 patients with CRCLM obtained one to two days before tumor resection. The control group comprised 140 healthy blood donors and 81 patients with various non-malignant gastrointestinal diseases. Raised arginase activity was observed in serum of 85% of CRCLM patients, whereas elevated levels of CEA and CA 19-9 were found in 63% and 42% of patients, respectively. The combination of CEA or CA 19-9 with the arginase assay improved their sensitivity, but the sensitivity of the combined parameters was not higher than that of the arginase test itself. AST and ALT activities were increased in about 30% of CRCLM patients. The specificity of the arginase test calculated for 221 control subjects was 76%. It can thus be concluded that the determination of serum arginase activity can be helpful in the diagnosis of patients with colorectal cancer liver metastases.

Characteristics of aminopeptidase activity from bovine brain microvessel endothelium.

Blood-brain barrier (BBB) aminopeptidase activity was investigated using an in vitro model consisting of primary cultures of brain microvessel endothelium. Using two different substrates, both membrane-bound and soluble aminopeptidases were found to be associated with brain endothelium. That the enzyme activity was aminopeptidase activity was confirmed with the competitive inhibition of substrate degradation by typical aminopeptidase inhibitors puromycin and bestatin. The aminopeptidase activity was also competitively inhibited by enkephalin, met-enkephalin, and leu-enkephalin. Results from parallel experiments with cerebral gray matter and kidney confirm assay conditions. This report supports previous suggestions that aminopeptidases of the enzymatic BBB may play a role in regulating levels of circulating neuropeptides in the cerebrovasculature.

Demonstration of acid hydrolase activity in primary cultures of bovine brain microvessel endothelium.

The existence of lysosomes and acid hydrolase activity was demonstrated in an in vitro blood-brain barrier (BBB) model comprising primary cultures of bovine brain microvessel endothelial cell (BMEC) monolayers. BMEC lysosomes were observed by the uptake of acridine orange and fluorophore-labeled acetylated low-density lipoprotein by fluorescence microscopy. Cytochemical localization of the acid hydrolase, sulfatase, and acid phosphatase (AcP) activities with light microscopy also revealed hydrolase-positive vacuoles or lysosomes that varied in number from cell to cell. BMEC monolayers were fractionated and biochemical assays of the sulfatase, AcP, and beta-galactosidase were performed. Significant activities of the acid hydrolases were found to be associated with lysosome and microsome fractions (69-77%). The majority of beta-galactosidase (approximately 48%) and total sulfatase (approximately 58%) activity was associated with the lysosome fraction of the BMECs. In contrast, approximately 52% of AcP activity was associated with the microsome fraction of the cells. The results of this study are consistent with the demonstration in vivo of acid hydrolases as potential factors in the endocytic pathway for transport of proteins through the BBB and as contributors to the BBB's enzymatic barrier function.

Sulfation in male reproductive organs. Bull and boar testis phenol sulfotransferases.

Phenol sulfotransferases (PST) from bull and boar testis were partially purified and characterized. A single form of PST adsorbed on DEAE-cellulose was found in the bull testis, whereas from boar testis two different peaks of PST activity were separated. The bull testis PST and both boar testis enzymes were active with p-nitrophenol and adrenalin. They all showed higher affinity to pNP than to adrenalin and were inhibited by these substrates at higher concentrations. Their optimal pH was at 8.5. Bull testis PST and boar PST II which were adsorbed on DEAE-cellulose were thermostable, whereas boar PST I was thermolabile. Those three PST forms differed in sensitivity to 2,6-dichloro-4-nitrophenol (DCNP), N-ethyl maleimide (NEM), iodoacetamide (IAA) and phenylglyoxal (PG). Bull and boar PST II were more rapidly inactivated in the presence of DCNP than boar PST I. In the presence of NEM, the--SH groups reagent, the bull phenol sulfotransferase and boar PST I lost their activity, whereas the activity of boar PST increased. Also iodoacetamide, another--SH group modificator, raised boar PST II activity and decreased boar PST I activity. DTT, which protects thiol groups, had an opposite effect on the enzymes studied than NEM. Phenylglyoxal, a reagent specific for arginine residues inhibited bull testis PST and both boar phenol sulfotransferases. Substrate protection experiments were also performed to determine the localization of reactive groups in bull and boar testis phenol sulfotransferases.

Extrahepatic sulfation of phenols. Bovine lung and intestinal phenol sulfotransferases.

Phenol sulfotransferases (PST) from bovine lung and small intestine were purified about 1000-fold. PST from bovine small intestine, similarly as the bovine lung enzyme, catalyzes sulfation of only exogenous phenols. A single thermostable form of PST, active with high concentrations of phenol (Km = 1.43 mM) was found in the small intestine. The effect of divalent cations on the activity of the two phenol sulfotransferases was determined. The molecular weight of the native enzymes was estimated as about 69,000 and subunit molecular weight determined by sodium dodecyl sulfate gel electrophoresis as 35,000. In double immunodiffusion tests the bovine lung PST showed antigenic identity with the bovine small intestine enzyme but complete immunological incompatibility with rat liver sulfotransferase.

Lung phenol sulfotransferases. Thermal stability of human and bovine enzymes.

Phenol sulfotransferase (PST) from human and bovine lung was purified about 1000-fold and the activity was measured with different acceptor substrates. Human lung PST catalyzes sulfation of both exo- and endogenous phenols, but the bovine lung enzyme only exogenous phenols. This difference in substrate specificity seems to be related to the presence of at least two different molecular forms of the enzyme: a thermostable and a thermolabile form in human lung, and two thermostable forms in bovine lung. Like the human platelet PST, the thermostable form from human lung is active with low concentrations of phenol (Km = 45 microM) and the thermolabile form with dopamine and high concentrations of phenol (Km = 909 microM). Bovine lung, which shows no catecholamine sulfating activity, contains two thermostable phenol sulfotransferases, both active with phenol but differing in their affinity to this substrate (Km = 40 microM and 335 microM, respectively).

D-cysteine as a selective precursor for inorganic sulfate in the rat in vivo. Effect of D-cysteine on the sulfation of harmol.

D-Cysteine, the unphysiological isomer of the sulfur containing amino acid L-cysteine, is not utilized for protein synthesis, glutathione synthesis or taurine production; it was tested as a selective precursor for inorganic sulfate, required for sulfation of xenobiotics. Both cysteine isomers were injected intravenously in the rat, in order to investigate their sulfoxidation to inorganic sulfate. The rates of sulfoxidation were very similar, so that stereospecificity for the amino acid seemed not to play a role. When the rats were fed a low-protein diet (LP-diet; containing only 8% casein as source of amino acids) the serum sulfate concentration decreased to about 20% of control. Under these circumstances the rate of sulfoxidation of both isomers was decreased to the same extent. In order to confirm that both cysteine isomers were equally efficient in providing inorganic sulfate for sulfation of xenobiotics, a constant infusion of harmol (a substrate for sulfation) was given to rats fed the LP-diet. Administration of L- or D-cysteine yielded similar increases in sulfation of harmol under these conditions. These results show that D-cysteine can be used to selectively enhance sulfate availability.

Glutathione conjugation in male reproductive system: studies on glutathione-S-transferase of bull and boar epididymis.

Male reproductive organs are extremely sensitive to the negative influence of toxic environmental factors as well as drugs, and until now not many attempts have been made at studying the detoxication enzymes and the relationship between the activity of those enzymes and spermatozoa fertility. In the present work we studied cytosolic glutathione-S-transferases (GST, EC 2.5.1.18) from different parts (head, corpus and tail) of bull and boar epididymis. We isolated two molecular forms of GST from each part of epididymis, characterized their biochemical properties and examined the mechanism of the catalyzed reaction. On the basis of their substrate specificity and isoelectric point, the isoforms were found to belong to the near neutral GST class mi. All examined GST forms exhibited higher affinity towards GSH than towards 1-chloro-2,4-dinitrobenzene (CDNB) and bull epididymis GST forms showed biphasic Lineweaver-Burk double reciprocal curves in the presence of GSH as a variable substrate. Boar epididymis anionic GST had the -SH groups both in the GSH and the CDNB binding place, whereas the cationic GST form--arginine residues in the CDNB binding place. Bull epididymis GST forms contained neither thiol nor arginine residues essential for catalytic activity.

Oligomeric structure of A1 arginase from rat liver and A4 from kidney. Difference in charge of subunits.

1. The predominant form of rat liver arginase, A1, and that of kidney, A4, were isolated and partially purified. 2. It was found that arginase A4, similarly as A1, has oligomeric structure. Either of the enzymes on EDTA treatment dissociates into inactive subunits of molecular weight 30 000 daltons. Addition of Mn2+ ions restores the activity and causes reassociation of subunits to the native form of 120 000 mol. wt. 3. The subunits of A4 differ considerably in electrophoretic mobility from subunits of A4, which probably is the reason why the native forms of the enzyme from kidney and liver differ in electrophoretic behaviour.

Purification and some properties of human heart arginase.

Arginase from extracts of human heart was purified about 1500-fold. In polyacrylamide-gel electrophoresis the enzyme migrated to the cathode at pH 5.5, showing very low mobility at pH 8.9. Molecular weight determined by gel filtration was 120 000. The Km for L-arginine was 5 mM. L-Ornithine and L-lysine were competitive inhibitors. The enzyme was completely inactivated by treatment with EDTA, and dissociated into subunits with mol.wt. of about 30 000. Addition of Mn2+ ions to the inactive subunits resulted in reappearance of the enzyme activity; the molecular weight of the reactivated enzyme corresponded to that of the native form.

Phenol sulphotransferase: purification and characterization of the rat kidney and stomach enzymes.

3'-Phosphoadenosine-5'-phosphosulphate-dependent enzymes that catalyse sulphation of p-nitrophenol have been purified from rat kidney and stomach mucosa by affinity chromatography on the p-hydroxyphenylacetic acid-agarose conjugate, by chromatography on DEAE-cellulose and Sephadex G-100. The phenol sulphotransferase (PST) from rat kidney had Mr of 69 000 and that of the stomach enzyme was 32 000. With p-nitrophenol as the sulphate acceptor, the pH optima were 6.4 for the stomach PST and 5.4 and 6.6 for the kidney enzyme. Both enzymes were inhibited by 2,6-dichloro-4-nitrophenol and phenylglyoxal, an arginine specific modifying reagent. Both enzymes readily sulphated p-nitrophenol, 2-naphthol, 1-naphthol and salicylamide and did not act on biogenic amines (e.g. epinephrine, norepinephrine, dopamine, serotonin), acid metabolites of catecholamines (e.g. 3,4-dihydroxyphenylacetic acid, homovanillic acid), and O-methylated metabolites of catecholamines. Only the stomach enzyme sulphated such catecholamine metabolites as homovanillic alcohol and 3-methoxy-4-hydroxyphenylglycol. In contrast to the brain enzyme, but similarly to the liver enzyme, the kidney and stomach phenol sulphotransferases appear to sulphate exogenous phenolic substrates in preference to potential endogenous substrates.

Arginase isoforms in human colorectal cancer.

Arginase (EC 3.5.3.1) activity was determined in 54 colorectal tissues obtained from patients with primary colorectal adenocarcinoma as well as in serum of 45 patients and 65 healthy individuals. In patients, the preoperative values of the mean serum arginase activity and the activity in colorectal tumors were much higher than in serum of healthy subjects and control tissues. Two isoforms of arginase, anionic and cationic, were identified in colorectal tissues (normal and cancerogenous), and only one, the cationic form, in serum. These arginases were different from the main human liver cationic arginase (pI 9.3). The anionic colorectal arginase was identical with the human liver anionic isoform (pI 7.7), and the cationic arginase from colorectal tissues and blood serum with the human kidney cationic enzyme (pI 8.9). The total activity and the level of protein of the cationic arginase in colorectal cancer was higher than in control tissue, and it was also higher in serum of patients with colorectal cancer than in healthy subjects. Thus, it can be concluded that the increased arginase activity in blood serum and colorectal cancer in studied patients was due to the raised level of the cationic arginase and this isoform seems to be a discriminating parameter for assessing the presence of colorectal cancer.

Biotransformation in monkey brain: coupling of sulfation to glutathione conjugation.

Phenol sulfotransferase (PST, EC 2.8.2.1) and glutathione-S-transferase (GST, EC 2.5.1.18), the phase II biotransformation enzymes inactivate many exo- and endogenous compounds. The effect of PST substrates (catecholamines, simple phenols, selected phenolic drugs) and PST products (phenolic sulfates) on GST activity was investigated to identify possible interactions between sulfation and glutathione conjugation in the brain. Two soluble forms of PST and two forms of GST were isolated from monkey (Rhesus macacus) brain cortex. Catecholamines, hypertensive and hypotensive drugs which are sulfated by monkey brain PSTs slightly inhibit the activity of brain GSTs. The greatest inhibitory effect was observed with neurotoxic compounds such as 6-OHDA and manganese. The commonly used analgesic drugs inhibit both GST forms. These enzymes are also inhibited by phenacetin, the precursor of paracetamol, and prototype salicylates such as sodium salicylate and acetylsalicylic acid. The effect of simple phenols and their sulfated metabolites on GST activity varies. The obtained results point to a possible interaction between sulfation and glutathione conjugation in vivo since many physiologically, therapeutically and toxicologically active compounds which are sulfated by brain phenol sulfotransferases may be bound by brain glutathione-S-transferases. These compounds may lose their activity (on being bound to GST) and expose the brain to the toxic electrophiles (by decreasing GST activity).

Substrate specificity and some properties of phenol sulfotransferase from human intestinal Caco-2 cells.

The phase II metabolic reactions, sulfation and glucuronidation, were studied in a human colon carcinoma cell line (Caco-2), which has been developed as a model of intestinal enterocytes. Phenol sulfotransferase (PST, EC 2.4.2.1) was isolated from Caco-2 cells cultured for 7, 14 and 21 days. The enzyme catalyzed the sulfation of both p-nitrophenol and catecholamines (e.g., dopamine) as well as most catecholamine metabolites. The affinity (Km) of PST for dopamine was much higher than for p-nitrophenol, and the specific activity of PST with both substrates increased with the age of the cells. The thermal stability of Caco-2 PST increased with cell age and was not dependent on the acceptor substrate used. The thermolabile PST from 7-day old cells was more sensitive to NEM than was the thermostable enzyme from 21-day old cells. No UDP-glucuronyltransferase (EC 2.4.1.17) activity was detected in 7-, 14- and 21-day old Caco-2 cells with any of the methods used.

[Tricyclic antidepressants as inhibitors of brain glutathione-S-transferase]. / Trójpierscieniowe leki przeciwdepresyjne jako inhibitory mózgowej transferazy glutationowej.

Tricyclic antidepressants, amitriptyline, doxepin--derivatives of cycloheptadiene as well as imipramine and clomipramine, derivatives of dibenzazepine inhibit the activity of glutathione-S-transferase pi isolated from different regions of human brain (parietal cortex, frontal cortex, brain stem). The inhibitory effect of studied drugs depends more on their chemical structure than on brain localization of the enzyme. All tricyclics bind nonspecifically to the effector site of glutathione-S-transferase (GST). The obtained results indicate that the inhibitory effect of tricyclic antidepressants on brain GST may decrease the efficiency of the enzymatic barrier, which protects brain against toxic electrophiles, and contribute in their adverse effects. On the other hand, brain GST may decrease the therapeutic effects of tricyclic antidepressants by binding them as ligands.