Determination of various 15N-enriched spermidines with gas chromatography-mass spectrometry

A novel method for the determination of all eight kinds of variously 15N-enriched spermidines including the natural one is described using gas chromatography-mass spectrometry. After strict assignments of nitrogen(s) in fragment ions split from pentafluoropropionyl derivative of spermidine with 20 eV impact, six fragments (P7 and P10 containing N1 and N4 of spermidine, P8 and P11 containing N4 and N8, and P14 and P15 containing N1, N4, and N8 as designated in the text) were found to be useful for calculating relative contents of the various spermidines. The calculation was carried out by a computer program with the input of 20 relative intensities observed at m/z 259-261, 273-275, 379-381, 393-395, 436-439, and 464-467. Reliability of the method was examined by measuring known mixtures of authentic spermidines. In an experiment testing reproducibility, an average coefficient of variation was 4.8% with a reasonable accuracy for the eight spermidines. Linearity of relative ratios of 15N-enriched spermidines to the natural one was assured with an average correlation coefficient of 0.996. The present method was applied for spermidine synthase reaction, and it was confirmed that the enzyme from rat prostate could not discriminate against 15N of putrescine.

Functionality of muscle proteins in gelation mechanisms of structured meat products

Recent advances in muscle biology concerning the discoveries of a large variety of proteins have been described in this review. The existence of polymorphism in several muscle proteins is now well established. Various isoforms of myosin not only account for the difference in physiological functions and biochemical activity of different fiber types or muscles, but also seem to differ in functional properties in food systems. The functionality of various muscle proteins, especially myosin and actin in the gelation process in modal systems which simulate structured meat products, is discussed at length. Besides, the role of different subunits and subfragments of myosin molecule in the gelation mechanism, and the various factors affecting heat-induced gelation of actomyosin in modal systems are also highlighted. Finally, the areas which need further investigation in this discipline have been suggested.

Differences between homogeneous spermidine synthases isolated from rat and pig liver

Spermidine synthase was purified to homogeneity from rat and pig liver by a method modified from a previously reported one using DEAE-Sepharose, S-adenosyl(5')-3-thiopropylamine-Sepharose affinity chromatography, Sephacryl S-300 gel filtration and polyacrylamide gel electrophoresis. No apparent difference between the two enzymes was observed in specific activity, molecular weight (74,000), or subunit composition (two subunits). However, significant differences were observed in their pI values, which were 5.16 for the pig enzyme and 5.34 for the rat enzyme, and their peptide maps. Amino acid compositions of the two enzymes were closely related, but differed significantly in some amino acids. In addition, the rat enzyme was more sensitive to inhibition by S-adenosyl-1,8-diamino-3-thiooctane than the pig enzyme.

Polyamine synthesis in mammalian tissues. Isolation and characterization of spermidine synthase from bovine brain

Spermidine synthase (EC 2.5.1.16) was purified to apparent homogeneity (about 11 000-fold) from bovine brain by affinity chromatography, with S-adenosyl-(5')-3-thiopropylamine linked to Sepharose as the adsorbent. The enzyme preparation was free from S-adenosylmethionine decarboxylase (EC 4.1.1.50) and spermine synthase (EC 2.5.1.22) activities. The native enzyme had an apparent Mr of 70 000, was composed of two subunits of equal size, and had an isoelectric point at pH 5.22. The apparent Km values for putrescine and decarboxylated adenosylmethionine [S-adenosyl-(5')-3-methylthiopropylamine] were 40 microM and 0.3 microM respectively. Cadaverine and 1,6-diaminohexane could replace putrescine as the aminopropyl acceptor, although the reaction rates were only 6% and 1% respectively of that obtained with putrescine. Ethyl, propyl and carboxymethyl analogues of decarboxy-S-adenosylmethionine could act as propylamine donors. Both the reaction products, spermidine and 5'-methylthioadenosine, were mixed-type inhibitors of the enzyme. On the basis of initial-velocity and product-inhibition studies, a ping-pong reaction mechanism for the spermidine synthase reaction was ruled out.

Determination of protonation sites in thermospermine and in some other polyamines by 15N and 13C nuclear magnetic resonance spectroscopy

The pK values of thermospermine, a novel asymmetric tetraamine (4,8-diazadodecane-1,12-diamine), have been determined for the first time by the conventional titration method with subsequent data analyses. It was found to be the most basic polyamine among naturally occurring tetraamines. The 15N NMR titration method was applied to determine its protonation site. Natural-abundance 15N magnetic resonance spectra of the polyamine have been recorded as a function of pH from its free to the protonated form. Its apparent pK values, as well as the intrinsic chemical shifts for each stage of protonation, have been calculated from the NMR titration curve by using a nonlinear least-squares method. The four protonation sites of thermospermine have been successfully determined to be N12, N1, N-8, and N-4 in that order from the free to the completely protonated form. In a similar manner the protonation sites of spermidine and two symmetric tetraamines, thermine and spermine, have been established. 13C NMR experiments for the four polyamines were almost consistent with those of 15N NMR. Owing to the much higher concentration of the polyamines furnished for NMR titration experiments, the pK values obtained by NMR were larger than those derived by the conventional titration methods.

Distribution of ornithine decarboxylase activity induced by 1 alpha,25-dihydroxyvitamin D3 in chick duodenal villus mucosa

The distribution of enzymes involved in polyamine synthesis and that of the polyamine levels were investigated in the duodenal mucosa of vitamin D-deficient chicks and those supplemented with 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3]. Duodenal epithelial cells were isolated sequentially from the villus tip to the crypt region using a nonenzymatic method. In vitamin D-deficient chicks, the activities of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase were markedly higher in the crypt cells than in the villus cells. Similar gradients were observed in the distribution of putrescine and spermidine. Six hours after iv administration of 625 ng 1 alpha,25-(OH)2D3, ODC activity and putrescine levels markedly increased both in the villus and crypt region. The rate of the increase in ODC activity and putrescine levels, however, was much higher in the villus than in the crypt region. Neither S-adenosylmethionine decarboxylase activity nor spermidine levels were affected by the treatment with 1 alpha,25-(OH)2D3. To investigate differential uptake of 1 alpha,25-(OH)2D3 in the duodenal mucosa, 0.1 nmol 1 alpha,25-(OH)2[3H]D3 with or without a 200-fold excess of unlabeled 1 alpha,25-(OH)2D3 was injected into rachitic chicks, and epithelial cells were sequentially isolated 2 h later. The radioactivity specifically incorporated in the nuclear fraction was distributed uniformly from the villus tip to crypt cells. The cytoplasmic receptor for 1 alpha,25-(OH)2D3 was similarly distributed in the crypt and villus cells. These results suggest that 1 alpha,25-(OH)2D3 plays a physiological role in cellular activities not only in the villus but also in the crypt region through polyamine biosynthesis.

Mode of action of 3-substituted propylamine cytotoxicity in culture cells

Cytotoxic effects on MDBK cells of various 3-substituted propylamines, including spermine and spermidine, were tested in culture in the presence of calf serum, and the possible mode of action was studied from the viewpoint of oxidative deamination leading to acrolein formation. The compounds were roughly classified in two groups with IC50 values of 0.1 and 0.4 mM under the conditions used. Phenyl derivatives of 3-substituted propylamines, 3-benzylaminopropylamine, and polyamines were included in the first group with IC50 values of 0.1 mM, and acrolein was liberated from these compounds after incubation with bovine plasma amine oxidase. Alkyl derivatives of 3-substituted propylamines (with IC50 values of 0.4 mM), on the other hand, were unable to release acrolein after the oxidative deamination, which was further confirmed by a lack of liberation of acrolein from the authentic 3-butoxypropanal. These observations indicated that both the acrolein originating from the 3-substituted propanals, and the propanal as such, were possibly involved in manifestation of the cytotoxicity of the 3-substituted propylamines. Thus, spermine and spermidine may exert their cytotoxic effects on the cells in vitro by a combination of two mechanisms involving acrolein and oxidized polyamines.

Comparison of efficacy of a new butyrophenone derivative, timiperone and perphenazine in schizophrenia by a multicentre controlled study

The efficacy of timiperone in schizophrenia as compared with perphenazine was assessed in a double-blind fashion in 205 patients throughout a 12-week treatment period. More than half of the subjects were chronic schizophrenics. Global improvement in the timiperone treatment group was superior to that in the perphenazine group in view of a lower rate of aggravation. With regard to overall safety and general usefulness rating, there were no significant differences between the two drug treatments. However, timiperone showed less frequency of excitability, irritability, anxiety and anorexia than perphenazine on occasions during the 12 week treatment period. From these results it may be concluded that the efficacy of timiperone could be superior or equivalent to that of perphenazine which has been confirmed to be of use as an antipsychotic.

Ornithine decarboxylase activity in chick duodenum induced by 1 alpha, 25-dihydroxycholecalciferol

The effect of cholecalciferol and its metabolites on ornithine decarboxylase activity was investigated in the duodenal mucosa of vitamin D-deficient chicks. The duodenal ornithine decarboxylase activity decreased in animals fed a vitamin D-deficient diet and its retarded activity was increased dose-dependently by a single injection of cholecalciferol. Among various metabolites of cholecalciferol tested, 1 alpha, 25-dihydroxycholecalciferol [ 1 alpha, 25 (OH)2D3] was the most potent stimulator. Stimulation of the enzyme activity was detected as early as 2h after intravenous administration of 1 alpha, 25 (OH)2D3 and a maximal value was attained at 6 h. The maximal value was 27 times higher than the control. In addition, treatment with 1 alpha 25 (OH)2D3 affected the duodenal content of polyamines. The content of putrescine increased to a value of three times that of the control 6 h after the hormone administration. The spermidine content did not change appreciably. The enhancement of duodenal ornithine decarboxylase activity by 1 alpha, 25 (OH)2D3 occurred in parallel with the enhancement of calcium absorption, which was first detected 3 h after the hormone administration. The enhancement appeared to be tissue-specific. It was observed in every intestinal segment, but was highest in the duodenum. Enzyme activity in other tissues was not influenced appreciably by 1 alpha, 25 (OH)2D3. These results clearly indicate that the duodenal biosynthesis of polyamines is regulated by 1 alpha, 25 (OH)2D3, suggesting the possibility that duodenal ornithine decarboxylase may be involved in the calcium absorption mechanism.

Molecular adaptability of carp myosin: a study of some physico-chemical properties and their comparison with those of rabbit myosin

During thermal inactivation, the addition of as low as M urea resulted in the reduction of delta G identical to barrier of the inactivation of carp myosin Ca2+-ATPase, whereas that of rabbit myosin remained unaffected. In the absence of urea, a four-hour incubation of carp myosin was accompanied by the release of light chains at 30 degrees C, a value 10 degrees C lower than that for rabbit myosin. Electron micrographs revealed that carp myosin forms artificial thick filaments, which were uniform in size and may differ in a few details from those of rabbit. Not only that helical content of carp myosin was about 4% less than those of rabbit myosin, but it showed more sensitivity to thermal and urea denaturation; and its reversibility upon subsequent cooling or removal of urea was rather poor. The loss in helicity of myosins by urea was a concentration- and temperature-dependent biphasic reaction, with the most obvious effect observed on carp myosin. That carp myosin has increased tendency of unfolding in urea solutions was confirmed by viscosity data and the exposure of thiols also. Even in the absence of urea more SH groups of carp myosin were incorporated by DTNB, and more epsilon-amino groups reacted with NQS. Carp myosin remained in solution till the modification of about 52 surface myosin remained in solution till the modification of about 52 surface amino groups, whereas no precipitation effect was noted in case of rabbit myosin. Neither amino-acid composition nor some parameters derived from it, such as average hydrophobicity polarity index and number of polar side chains, revealed any difference pertinent to the relative stability of the two myosins. On the contrary, the contractile efficiency of carp myosin in the near physiological range was high and thus inversely related with the thermostability. This relationship along with the above evidence has been regarded to demonstrate the adaptability of carp myosin through a loose molecular conformation, which has probably been achieved by the addition of weak interactions in the course of evolution.