Polyamine starvation causes accumulation of cadaverine and its derivatives in a polyamine-dependent strain of Chinese-hamster ovary cells

The Molecular and Physiological Effects of Protein-Derived Polyamines in the Intestine

Consumption of a high-protein diet increases protein entry into the colon. Colonic microbiota can ferment proteins, which results in the production of protein fermentation end-products, like polyamines. This review describes the effects of polyamines on biochemical, cellular and physiological processes, with a focus on the colon. Polyamines (mainly spermine, spermidine, putrescine and cadaverine) are involved in the regulation of protein translation and gene transcription. In this, the spermidine-derived hypusination modification of EIF5A plays an important role. In addition, polyamines regulate metabolic functions. Through hypusination of EIF5A, polyamines also regulate translation of mitochondrial proteins, thereby increasing their expression. They can also induce mitophagy through various pathways, which helps to remove damaged organelles and improves cell survival. In addition, polyamines increase mitochondrial substrate oxidation by increasing mitochondrial Ca2+-levels. Putrescine can even serve as an energy source for enterocytes in the small intestine. By regulating the formation of the mitochondrial permeability transition pore, polyamines help maintain mitochondrial membrane integrity. However, their catabolism may also reduce metabolic functions by depleting intracellular acetyl-CoA levels, or through production of toxic by-products. Lastly, polyamines support gut physiology, by supporting barrier function, inducing gut maturation and increasing longevity. Polyamines thus play many roles, and their impact is strongly tissue- and dose-dependent. However, whether diet-derived increases in colonic luminal polyamine levels also impact intestinal physiology has not been resolved yet.

Development of a serum-free culture medium for the large scale production of recombinant protein from a Chinese hamster ovary cell line

A serum-free medium, WCM5, has been developed for the large scale propagation of CHO (Chinese hamster ovary) cells which express recombinant protein using dihydrofolate reductase as a selectable marker. WCM5 was prepared by supplementing Iscoves medium without lecithin, albumin or transferrin with a number of components which were shown to benefit growth. WCM5 medium contained 5 mg l(-1) human recombinant insulin (Nucellin) but was otherwise protein-free. CHO 3D11(*) cells which had been engineered to express a humanised antibody, CAMPATH(*)-1H, were routinely grown using serum-containing medium. From a seeding density of 10(5) cells ml(-1), cells grown in static culture with serum reached a maximal cell density of 6.5×10(5) cells ml(-1) after 6 days in culture and produced a maximal antibody concentration of 69 mg l(-1) after 11 days in culture. CHO 3D11(*) cells grown with serum were washed in serum-free medium then cultured in WCM5 medium. Following a period of adaptation the cell growth and product yield was superior to that achieved with serum-containing medium. CHO cells producing CAMPATH-1H grown in an 8000 l stirred bioreactor seeded with 2×10(5) cells ml(-1) reached a maximal viable cell density of 2.16×10(6) cells ml(-1) after 108 h in culture and a maximal antibody concentration of 131.1 mg l(-1) after 122 h in culture.

The first agmatine/cadaverine aminopropyl transferase: biochemical and structural characterization of an enzyme involved in polyamine biosynthesis in the hyperthermophilic archaeon Pyrococcus furiosus

We report here the characterization of the first agmatine/cadaverine aminopropyl transferase (ACAPT), the enzyme responsible for polyamine biosynthesis from an archaeon. The gene PF0127 encoding ACAPT in the hyperthermophile Pyrococcus furiosus was cloned and expressed in Escherichia coli, and the recombinant protein was purified to homogeneity. P. furiosus ACAPT is a homodimer of 65 kDa. The broad substrate specificity of the enzyme toward the amine acceptors is unique, as agmatine, 1,3-diaminopropane, putrescine, cadaverine, and sym-nor-spermidine all serve as substrates. While maximal catalytic activity was observed with cadaverine, agmatine was the preferred substrate on the basis of the k(cat)/K(m) value. P. furiosus ACAPT is thermoactive and thermostable with an apparent melting temperature of 108 degrees C that increases to 112 degrees C in the presence of cadaverine. Limited proteolysis indicated that the only proteolytic cleavage site is localized in the C-terminal region and that the C-terminal peptide is not necessary for the integrity of the active site. The crystal structure of the enzyme determined to 1.8-A resolution confirmed its dimeric nature and provided insight into the proteolytic analyses as well as into mechanisms of thermal stability. Analysis of the polyamine content of P. furiosus showed that spermidine, cadaverine, and sym-nor-spermidine are the major components, with small amounts of sym-nor-spermine and N-(3-aminopropyl)cadaverine (APC). This is the first report in Archaea of an unusual polyamine APC that is proposed to play a role in stress adaptation.

Formation of cadaverine derivatives in Saccharomyces cerevisiae

The higher homologues of cadaverine, aminopropylcadaverine (APC) and N,N-bis(3-aminopropyl)cadaverine (3APC) were formed by a wild-type strain of Saccharomyces cerevisiae, and by two mutant strains, spe 3-1 and spe 4-1, exhibiting point mutations in the genes for spermidine synthase and spermine synthase, respectively. This, together with the incomplete inhibition of APC and 3APC formation in the presence of inhibitors of S-adenosylmethionine decarboxylase and spermidine synthase, suggests that the cadaverine derivatives are formed partly by the operation of a different route. However, the yeast strains were unable to utilise [14C]aspartate and lysine to form APC and 3APC. Since the ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO) greatly reduced the formation of APC and 3APC, it is suggested that these compounds are formed preferentially in these yeast strains from cadaverine formed by ODC. APC and 3APC formation in the yeast strains was increased substantially following exposure to 37 degrees C for 2 h.

A new polyamine 4-aminobutylcadaverine. Occurrence and its biosynthesis in root nodules of adzuki bean plant Vigna angularis

Root nodules of adzuki bean plant (Vigna angularis) contained a novel polyamine. The chemical structure of the new polyamine was determined to be NH2(CH2)5-NH(CH2)4NH2 (4-aminobutylcadaverine) based on gas chromatography-mass spectrometry. The occurrence of 4-aminobutylcadaverine was specific to the root nodules, since the unusual triamine was not detected in other organs of the adzuki bean plant. Bacteroids, isolated from root nodules, contained both sym-homospermidine and 4-aminobutylcadaverine, whereas the plant cytosol fraction contained large quantities of putrescine and cadaverine. A cell-free extract of bacteroids showed the ability to form this triamine from putrescine and cadaverine under the presence of NAD+ and K+. 1,3-Diaminopropane and NADH were inhibitory for the synthesis of both sym-homospermidine and 4-aminobutylcadaverine. [1,4-15N]Putrescine was incorporated not only into sym-homospermidine but also into 4-aminobutylcadaverine by the cell-free extract of bacteroids when incubated with excess cadaverine. Analysis of the fragment ion peaks in the 15N-enriched 4-aminobutylcadaverine indicated the transfer of a aminobutyl moiety to the amino terminus of cadaverine. These results suggest that, in adzuki bean, 4-aminobutylcadaverine is formed through the action of homospermidine synthase in nodule bacteroids under a cadaverine-rich environment.

Sequestered end products and enzyme regulation: the case of ornithine decarboxylase

The polyamines (putrescine, spermidine, and spermine) are synthesized by almost all organisms and are universally required for normal growth. Ornithine decarboxylase (ODC), an initial enzyme of polyamine synthesis, is one of the most highly regulated enzymes of eucaryotic organisms. Unusual mechanisms have evolved to control ODC, including rapid, polyamine-mediated turnover of the enzyme and control of the synthetic rate of the protein without change of its mRNA level. The high amplitude of regulation and the rapid variation in the level of the protein led biochemists to infer that polyamines had special cellular roles and that cells maintained polyamine concentrations within narrow limits. This view was sustained in part because of our continuing uncertainty about the actual biochemical roles of polyamines. In this article, we challenge the view that ODC regulation is related to precise adjustment of polyamine levels. In no organism does ODC display allosteric feedback inhibition, and in three types of organism, bacteria, fungi, and mammals, the size of polyamine pools may vary radically without having a profound effect on growth. We suggest that the apparent stability of polyamine pools in unstressed cells is due to their being largely bound to cellular polyanions. We further speculate that allosteric feedback inhibition, if it existed, would be inappropriately responsive to changes in the small, freely diffusible polyamine pool. Instead, mechanisms that control the amount of the ODC protein have appeared in most organisms, and even these are triggered inappropriately by variation of the binding of polyamines to ionic binding sites. In fact, feedback inhibition of ODC might be maladaptive during hypoosmotic stress or at the onset of growth, when organisms appear to require rapid increases in the size of their cellular polyamine pools.

Mutant strain of Chinese hamster ovary cells with no detectable ornithine decarboxylase activity

We previously described an arginase-deficient, polyamine-dependent Chinese hamster ovary cell line which grows in serum-free medium. From this strain we isolated a new mutant strain that has no detectable catalytic ornithine decarboxylase activity. The mutant cells contain, however, immunoreactive ornithine decarboxylase-like protein roughly in the same quantity as the parent strain. The mutant and the parent cell line strains also contain similar amounts of ornithine decarboxylase-mRNA hybridizable to a specific cDNA. If polyamines are omitted from the medium, proliferation of the mutant cells is considerably retarded and ceases in 6 to 10 days. Addition of ornithine or alpha-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, has no effect on these cells. Putrescine and spermidine decreased in the mutant cells to undetectable levels during polyamine starvation, whereas spermine was reduced to 1/5th of that found in the control cultures. Polyamines appear to be indispensable for the mutant strain, but this was obvious only after the amount of polyamines, found as impurities in bovine serum albumin used in the medium, was reduced by dialysis to 10(-12) M. Because sera contain polyamines, the ability of the mutant strain to grow in serum-free medium is a great advantage in elucidation of the mechanisms of polyamine function.

Mutant strain of Chinese hamster ovary cells with no detectable ornithine decarboxylase activity

We previously described an arginase-deficient, polyamine-dependent Chinese hamster ovary cell line which grows in serum-free medium. From this strain we isolated a new mutant strain that has no detectable catalytic ornithine decarboxylase activity. The mutant cells contain, however, immunoreactive ornithine decarboxylase-like protein roughly in the same quantity as the parent strain. The mutant and the parent cell line strains also contain similar amounts of ornithine decarboxylase-mRNA hybridizable to a specific cDNA. If polyamines are omitted from the medium, proliferation of the mutant cells is considerably retarded and ceases in 6 to 10 days. Addition of ornithine or alpha-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, has no effect on these cells. Putrescine and spermidine decreased in the mutant cells to undetectable levels during polyamine starvation, whereas spermine was reduced to 1/5th of that found in the control cultures. Polyamines appear to be indispensable for the mutant strain, but this was obvious only after the amount of polyamines, found as impurities in bovine serum albumin used in the medium, was reduced by dialysis to 10(-12) M. Because sera contain polyamines, the ability of the mutant strain to grow in serum-free medium is a great advantage in elucidation of the mechanisms of polyamine function.

Polyamine starvation prolongs the S and G2 phases of polyamine-dependent (arginase-deficient) CHO cells

This study analyzes the effects of polyamine starvation on cell cycle traverse of an arginase-deficient CHO cell variant (CHO-A7). These cells grow well in serum-free medium, provided that it contains ornithine or polyamines or both. In the absence of ornithine or polyamines or both, the CHO-A7 cells develop severe polyamine deficiency and, as a consequence, grow more slowly. When grown to a stationary phase in the presence of ornithine or putrescine or both, the CHO-A7 cells became arrested in G0/early G1. However, when starved for ornithine and polyamines, they accumulated in the S and G2 phases. Ornithine and polyamine starvation of CHO-A7 cells causes an increase in ornithine decarboxylase activity. When this increase was prevented by treatment with DL-alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, growth was further suppressed, and a greater fraction of cells were found in the S and G2 phases of the cell cycle.

Polyamine starvation prolongs the S and G2 phases of polyamine-dependent (arginase-deficient) CHO cells

This study analyzes the effects of polyamine starvation on cell cycle traverse of an arginase-deficient CHO cell variant (CHO-A7). These cells grow well in serum-free medium, provided that it contains ornithine or polyamines or both. In the absence of ornithine or polyamines or both, the CHO-A7 cells develop severe polyamine deficiency and, as a consequence, grow more slowly. When grown to a stationary phase in the presence of ornithine or putrescine or both, the CHO-A7 cells became arrested in G0/early G1. However, when starved for ornithine and polyamines, they accumulated in the S and G2 phases. Ornithine and polyamine starvation of CHO-A7 cells causes an increase in ornithine decarboxylase activity. When this increase was prevented by treatment with DL-alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, growth was further suppressed, and a greater fraction of cells were found in the S and G2 phases of the cell cycle.

Biochemistry of the polyamines

The naturally-occurring polyamines exist in the free form, as N-acetyl derivatives and bound to protein. Their biosynthesis is subject to sensitive control, particularly of ornithine decarboxylase. This enzyme may be multifunctional and a key regulatory protein. Studies, principally with selective inhibitors, have elucidated the roles of polyamines in cell proliferation. Oxidized polyamines, in contrast, can be potent mitotic inhibitors. These effects are reviewed in terms of their chemistry and biochemistry. Their principal distinctions are that they can be made or degraded intracellularly, they can associate electrostatically with macromolecules by means of their spaced cationic groups, and these can be readily converted to covalent bonds.