The effect of indole-3-carbinol, an aflatoxin B1 hepatocarcinoma inhibitor, and other indole analogs on the rainbow trout hepatic mixed function oxidase system

Rainbow trout were fed diets containing 3.4 mmol of indole-3-carbinol, indole-3-ethanol, indole-3-aldehyde, or indole-3-acetic acid in 100 g salmon oil/kg diet for 3 weeks. The indoles did not increase hepatic microsomal cytochrome(s) P-450 or P-448 nor induce the associated mixed function oxidase enzyme activities as measured by ethoxyresorufin-O-deethylase (EROD) and benzphetamine-N-demethylase activities. Indole-3-carbinol did not alter the in vitro metabolism of aflatoxin B1 to aflatoxicol and aflatoxin M1; but the other indoles did suppress the formation of aflatoxin M1 from aflatoxin B1. The results suggest that the mechanism by which indole-3-carbinol protected rainbow trout from aflatoxin B1 (AFB1) hepatocarcinogenesis was not via the alteration of the mixed function oxidase system.

Purification and characterization of a fibrinogenase from the venom of Western Diamondback rattlesnake (Crotalus atrox)

A fibrinogenolytic enzyme was isolated from the venom of Western Diamondback rattlesnake (Crotalus atrox) by a three-step procedure involving gel filtration and anion-exchange chromatography. The molecular weight was estimated as 22 900 by SDS-polyacrylamide gel electrophoresis. The isoelectric point was found to be pH 4.65. The enzyme rapidly destroyed the ability of bovine fibrinogen to form a clot on incubation with thrombin. Incubation of fibrinogen with the fibrinogenolytic enzyme for 5 min resulted in the disappearance of the beta-chain of fibrinogen and the appearance of lower molecular weight fragments. Thus the enzyme can be classified as a beta-fibrinogenase. However, on prolonged incubation of the fibrinogen there was also a partial digestion of the alpha-chain. The fibrinogenase showed no activity towards fibrin or casein or arginine esters. The fibrinogenolytic activity was inhibited by phenylmethanesulphonyl fluoride (PMSF) but was unaffected by EDTA.

An improved method of isolation of rat pancreatic prokallikrein. Characterization of the zymogen and of the kallikrein produced by trypsin activation

A prokallikrein was purified 1600-fold from rat pancreatic tissue in an overall yield of 40% by a simple four-stage procedure. The final and crucial step was immunoaffinity chromatography utilizing antibody raised to a very small amount of prokallikrein. Both the pure zymogen and the active kallikrein generated from it by trypsin activation are single chain species with Mr values of 38400 +/- 300 and 35500 +/- 400, respectively. Valine is the N-terminal amino acid residue of prokallikrein. The zymogen was comparatively stable both to autoactivation and denaturation with respect to temperature and pH. The kallikrein produced by trypsin activation of the zymogen was similar in some of its catalytic properties to the kallikrein purified from autolyzed rat pancreas but the two species differed in their susceptibility to substrate activation.

Aflatoxin B1 metabolism and DNA binding in isolated hepatocytes from rainbow trout (Salmo gairdneri)

The metabolism of aflatoxin B1 (AFB1) was examined in freshly isolated hepatocytes from rainbow trout. Intracellular DNA adduct formation was linearly related to AFB1 dose, and qualitatively similar to adducts formed in vivo. The rate of adduct accumulation was constant during the first hour following completion of the preparation, after which an increase and gradual decrease in rate routinely occurred. The relative rates of production of the major unbound AFB1 metabolites aflatoxicol, aflatoxin M1, and polar conjugates, also remained constant over the first hour of preparation age, but subsequently changed in a manner consistent with the changes in DNA binding. The common solvent vehicles ethanol and dimethyl sulfoxide were shown to seriously perturb AFB1 metabolism and DNA binding even at levels less than 1%. A simple method is reported for removal of ethanol prior to introduction of hepatocytes for incubation with AFB1. The influence of cell concentration was also examined. DNA binding and relative distribution of AFB1 metabolites showed little or no dependence in the range 1-6 x 10(6) cell/ml, but were substantially altered above 10(7) cells/ml. Under defined conditions, studies in isolated hepatocytes appear to reflect in vivo cell capabilities for AFB1 metabolism.

Carcinogen aflatoxin B1 is located preferentially in internucleosomal deoxyribonucleic acid following exposure in vivo in rainbow trout

The purpose of this work was to investigate the distribution in chromatin of deoxyribonucleic acid (DNA) adducts of aflatoxin B1, following exposure in vivo. Rainbow trout were injected intraperitoneally with radiolabeled aflatoxin B1, a potent procarcinogen known to readily induced hepatocellular carcinomas in these fish. After maximum incorporation, liver nuclei were prepared and digested with micrococcal nuclease. Mono-, di-, and trinucleosomal fractions were purified from several stages of nuclease digestion, and the lengths and specific activities of their DNA were determined. The results indicate that aflatoxin B1 is approximately 5 times as likely on a per nucleotide basis to localize on internucleosomal (linker) DNA as on nucleosomal core DNA in this system.

Purification and partial characterisation of a bovine kidney aminotripeptidase (capable of cleaving prolyl-glycylglycine)

An enzyme was purified 163-fold in an 8.2% yield from bovine kidney. The specific activities of the pure preparation against L-prolyl glycylglycine and L-alanyl glycylglycine were found to be 244.5 and 578 micron Moles substrate hydrolyzed per min per mg protein respectively. The molecular weight of the enzyme was estimated on gel filtration to be 55,000. The isoelectric point was recorded to be pH 5.2. A preliminary study of substrate specificity showed that the enzyme preferentially hydrolyzed tripeptides of the type X-glycylglycine. The enzyme was tentatively identified as a tripeptide aminopeptidase (alpha aminoacyldipeptide hydrolase, EC 3.4.11.4).

The purification of a bovine kidney enzyme which cleaves melanocyte-stimulating hormone-release inhibiting factor

An enzyme which catalyzes the hydrolysis of L-prolyl-L-leucylglycinamide, the factor which inhibits the release of melanocyte-stimulating hormone, was purified 189-fold from bovine kidney in a 5% yield. The molecular weight of the enzyme on gel filtration was estimated to be 300 000 and its isoelectric point was found to be pH 4.1. The single component seen on sodium dodecyl sulphate-gel electrophoresis was estimated to have a molecular weight of 56 000, indicating that the native enzyme may be a pentamer or hexamer. The enzyme could clearly be distinguished from other prolyl-cleaving enzymes.

Gene duplication in tetraploid fish: model for gene silencing at unlinked duplicated loci

Several groups of fishes, including salmonids and catastomids, appear to have originated through genome duplication events. However, these two groups retain approximately 50% of the loci examined as functioning duplicates, despite the passage of 50 million years or more of mutation and selection. Although other effects are not excluded, this apparently slow rate of duplicate silencing can be explained in terms of the effects of selection against defective double homozygotes to unlinked duplicates. We have derived a computer simulation of genetic drift that affords direct evaluation of the effects of population size (N), mutation rate (micron), initial allele frequencies, back mutation, fitness, and time on the probability of fixation for null alleles at unlinked duplicate loci. The results show that this probability is approximately linearly related to population size for N greater than or equal to 10(3). Specifically, for naive populations, the time for 50% probability of gene silencing is approximately equal to 15N + micron-3/4 generations. The retention of 50% of the loci as functional duplicates may therefore result from the large effective size of salmonid and catastomid populations. The results also show that, under most conditions for populations of 2000--3000 or larger, unlinked duplicate loci will be sustained in the functional state longer than tandem (linked) duplicates and hence are available for evolution of new functions for a longer time.

The immunological similarity of rat glandular kallikreins

The immunological properties of the submandibular kallikrein, urinary kallikrein, pancreatic kallikrein and pancreatic prekallikrein of the rat were studied by immunodiffusion, immunoelectrophoresis and radioimmunoassay. Although they behaved differently electrophoretically, all the antigens showed identical immunological behaviour. The implications of this are discussed.

Gene duplication in salmonid fishes: evidence for duplicated but catalytically equivalent A4 lactate dehydrogenases

Skeletal muscle tissues from many species of salmonid fish are known to exhibit a set of three of five isozymes for A4-type lactate dehydrogenase (L-lactate: NAD oxidoreductase, E.C. 1.1.1.27), but the genetic basis for this isozyme system has not previously been assessed. This isozyme system was purified to homogeneity from salmon (Oncorhynchus tshawytscha) and shown to be composed of two polypeptides. Aalpha and Abeta, in binomial tetrameric combinations. Amino acid analysis revealed that Aalpha and Abeta are closely related but genetically distinct proteins, and thus are coded for the recently duplicated structural loci. Catalytic studies on the purified intact salmon isozyme system and on the isozymically pure Aalpha4 and Abeta4 homotetramers from brown trout (Salmo trutta) revealed no significant differences in catalytic properties among these enzymes, suggesting equivalent catalytic function of Aalpha and Abeta. These results, in combination with studies on polypeptide and isozyme ratios, suggest that one of the duplicated loci in salmon may be drifting toward a nonfunctional state by accumulation of mutations in regulatory DNA rather than in the structural gene itself.

Automated sequencing of insoluble peptides using detergent. Bacteriophage fl coat protein

Peptides which are highly nonpolar and insoluble under moderate conditions of pH and ionic strength cannot be subjected to automated sequence analysis. We report a method for solubilization of one such peptide, bacteriophage fl coat protein, by chemical modification in the presence of sodium dodecyl sulfate. Following this treatment the 50-residue peptide was degraded stepwise in an automated sequenator using a single cleavage Quadrol program with high repetitive yield through residue 47. We also report a modified program using detergent incorporated into dimethylallylamine buffer which permitted sequencing with high repetitive yields for at least the first 18 residues of the unmodified and otherwise highly insoluble coat protein. The presence of detergent caused no observable difficulties in detection of residues by gas chromatography, thin layer chromatography, or amino acid analysis.

Immunological properties of nerve growth factors

Antisera were raised against nerve growth factors isolated from mouse salivary gland and five venoms representative of the three main families of poisonous snakes. Immunochemical cross-reactivity was assessed from the ability of the antisera to inhibit the biological activities of the heterologous antigens. The high and low molecular weight forms of the salivary gland factors were found to be immunologically identical but distinct from the snake venom factors. The snake venom factors, on the other hand, were immunologically closely related to each other but not identical.

The Number of Genes for Lactate Dehydrogenase in Salmonid Fishes

Rainbow trout (Salmo gairdneri) that show polymorphism at the ldhHα locus for liver lactate dehydrogenase (LDH) (L-lactate: NAD oxidoreductase, EC 1.1.1.27) have been examined electrophoretically and immunologically. These results show that the ldhHα locus is active in two possible allelic forms, ldhHαA and ldhHαB, in many tissues such as heart, liver, kidney, eye, red blood cell, brain, and pyloric caeca. Quantitative microcomplement fixation tests support the contention that HαA and HαB subunits are allelic variants. These results, combined with electrophoretic studies on brook trout (Salvelinus fontinalis) polymorphic at the ldhHβ locus, lead us to conclude that all isozymes for LDH in salmonid fishes can be accounted for by the activity of four, and possibly five structural loci: ldhHα, ldhHβ, ldhC, ldhMα, and possibly ldhMβ. These results are in contrast to previous suggestions that the multiple lactate dehydrogenases of trout are encoded by 8 or 10 structural genes per haploid genome.

Purification and properties of a kininogenin from the venom of Vipera ammodytes ammodytes

A kininogenin (EC 3.4.21.8) was purified from the venom of Vipera ammodytes ammodytes (European sand viper) by a combination of gel filtration and ion-exchange chromatography. The enzyme is approximately six times more active than bovine trypsin in its ability to release vasoactive peptides from a plasma precursor. The kininogenin is a glycoprotein containing 18-20% by weight of carbohydrate. It showed a mol. wt. of 40500 on gel filtration. Gel electrophoresis of the reduced sample in the presence of sodium dodecyl sulphate and 2-mercaptoethanol revealed the presence of two major components of mol.wt. 34300 and 31300. The heterogeneity, which was also observed on disc electrophoresis, was removed by incubation with neuraminidase. After incubation with neuraminidase the kininogenin retained full enzymic activity and possessed an isoelectric point of pH7.2. The carbohydrate content has been decreased to 10% by weight, and the single component seen on electrophoresis in the presence of sodium dodecyl sulphate and 2-mercaptoethanol corresponded to a mol.wt. of 29500.

Purification and specificity of prolyl dipeptidase from bovine kidney

Prolyl dipeptidase (iminodipeptidase, L-prolyl-amino acid hydrolase, EC 3.4.13.8) was purified 180-fold from bovine kidney. The enzyme which was obtained in a 10% yield was completely separated from a number of known kidney peptidases including an enzyme of very similar substrate specificity, proline aminopeptidase (L-prolyl-peptide hydrolase, EC 3.4.11.5). The specific activity of the enzyme with L-prolylglycine as substrate is 1600 units of activity per mg protein. Optimum activity of the enzyme is at pH 8.75 and the molecular weight on gel filtration was estimated to be 100 000. The isoelectric point of the enzyme is pH 4.25. Studies of substrate specificity showed that the enzyme preferentially hydrolyzes dipeptides and dipeptidyl amides with L-proline or hydroxy-L-proline at the N-terminus. Longer chain substrates with N-terminal proline were not hydrolyzed.

Lactate dehydrogenase isozymes of salmonid fish. Evidence for unique and rapid functional divergence of duplicated H-4 lactate dehydrogenases

Salmonid fish, as a result of total genome duplication, have two genes, Ldh H and Ldh H', coding for polypeptides H and H', respectively, both of which have been shown in their tetrameric forms to be immunologically related to the classical H-4 lactate dehydrogenase isozyme of higher vertebrates (Bailey, G. S., and Wilson, A. C. (1968) J. Biol. Chem. 243,5843). The H-4 and H'-4 isozymes have now been highly purified from quinnat salmon, and their chemical, physical, immunological, and catalytic properties examined, and compared to the M-4 isozyme of salmon. The two proteins H-4 and H'-4 are shown to be very similar in amino acid composition, but significant differences in a few residues suggest differences in amino acid sequences. This suggestion was born out by quantitative immunological experiments in which the H-4 and H'-4 isozymes were shown to be about as different from each other as are the H-4 lactate dehydrogenases of chicken and duck. This suggests that the gene duplication event in salmon which give rise to two Ldh H genes occurred approximately 80 to 100 million years ago. The H'-4 lactate dehydrogenase which has risen from this duplication in salmon is shown to be somewhat intermediate between H-4 and M-4 in thermal stability, and in all catalytic properties examined, including substrate optima, Michaelis constants, and susceptibility to inhibition by high levels of substrate. In particular the H'-4 isozyme is almost exactly intermediate between H-4 and M-4 in its resistance to product inhibition by lactate, the catalytic parameter suggested to be of major functional importance to M-4 lactate dehydrogenase isozymes (Stambaugh, R., and Post D. (1966) J. Biol. Chem. 241,1462). Further, tissue distribution of these isozymes in salmon and trout are shown to be unusual. The M-4 isozyme salmon and trout are shown to be unusual. The M-4 isozyme occurs in very few tissues in detectable levels. It is the H-4 and H'-4 rather than H-4 and M-4, which occur in independently variable but significant levels in most tissues examined. Thus the H'-4 isozyme, despite its very close structural similarity to H-4 appears to possess functional properties which are different from either H-4 or M-4 in salmon, and some properties are midway between the two. This finding, together with the unusual tissue distribution of these isozymes, suggests that salmon with H'-4 lactate dehydrogenase is evolving to function catalytically in the absence of a balanced H-4-M-4 isozyme complement in most tissues. This balance seems to be met in most tissues by combinations of H-4 and H'-4,

Phenoxyethanol: protein preservative for taxonomists

Pieces of chicken heart or skeletal muscle were placed in a dilute solution of the antimicrobial agent 2-phenoxyethanol and stored at room temperature. Under these conditions, the serum albumin, lactate dehydrogenase, and malate dehydrogenase in these tissues survived in easily detectable amounts for at least 2 weeks. The surviving proteins appeared to be identical with those of fresh tissues in physical, catalytic, and immunological properties. Phenoxyethanol also preserved heart and muscle proteins of representatives of other vertebrate classes. Tissue samples collected in the analysis by biochemical taxonomists.