The decarboxylation of <i>S</i>-adenosylmethionine by detergent-treated extracts of rat liver

Wilson, J. H. P.; Corti, Angelo; Hawkins, M.; Williams-Ashman, H.G.; Pegg, Anthony E.

doi:10.1042/bj1800515

Cited by 17 publications

(5 citation statements)

References 29 publications

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“…108,000, 88,000, and 68,000, respectively (23). The corn seedling enzyme has been described as having a mol wt of approximately 25,000, estimated by gel filtration on Sephadex G-200 (20). The estimation reported in the present paper was conducted on Sephacryl S-300, which yielded a value for spermidine synthase, i.e.…”

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S-Adenosylmethionine Decarboxylase and Spermidine Synthase from Chinese Cabbage

Yamanoha

Cohen²

1985

Plant Physiol.

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The enzyme, S-adenosylmethionine (SAM) decarboxylase (EC 4.1.1.50), has been demonstrated in leaves of Chinese cabbage, (Brassica pekinensis var Pak Choy). All of the enzyme can be found in extracts of the protoplasts obtained from the leaves of growing healthy or virusinfected cabbage. The protein has been purified approximately 1500-fold in several steps involving ammonium sulfate precipitation, affinity chromatography, and Sephacryl S-300 filtration. The reaction catalyzed by the purified enzyme has been shown to lead to the equimolar production of CO2 and of decarboxylated S-adenosylmethionine (dSAM). The K, for SAM is 38 micromolar. The reaction is not stimulated by Mg' or putrescine, and is inhibited by dSAM competitively with SAM. It is also inhibited strongly by methylglyoxal bis(guanylhydrazone). The enzyme, spermidine synthase (EC 2.5. of Lathynrs sativus (19), a small amount of activity was concentrated and purified by affinity chromatography. The stoichiometry of the reaction was not determined nor was the amount of activity related to the amount of spermidine synthesized in the plant. This activity, as well as that found in mung bean sprouts (6), was shown to be Mge' dependent, as are some bacterial SAM decarboxylases. The levels ofbiosynthetic activity detected in extracts of these plant materials were extremely low and may have arisen from bacterial contamination. On the other hand, the activity of SAM decarboxylase isolated from corn seedlings (20) has been reported to be independent of Mge' or putrescine, as is the enzyme we have now isolated from Chinese cabbage. Nevertheless, the low level of activity of the corn enzyme, by comparison to the amount of spermidine found in plants, has similarly raised the problem of the significance of this activity.One product of the SAM decarboxylase reaction, dSAM, is difficultly available. Despite its recent synthesis, an extinction coefficient has not been published (15) and a direct measurement of the stoichiometry of the decrease of SAM and appearance of dSAM has not previously been attempted. For this reason the decarboxylation reaction catalyzed by several presumed SAM decarboxylases cannot be considered unequivocal. The compound, dSAM, was generated from SAM by the Escherichia coli enzyme in 87% yield, calculated on the assumption that dSAM had an extinction coefficient identical to that of SAM (21, 28). Low yields of dSAM via enzymatic decarboxylation of SAM, arise from the relatively high Km of SAM in the reaction, as well as feedback inhibition by dSAM. Thus, stoichiometry in the decarboxylation has been demonstrated only by coupling spermidine synthase and putrescine to the system to trap the aminopropyl of dSAM in spermidine and to compare the yield of this triamine to that of CO2 (12,14).A newly developed analytical system has been applied to the determination of picomole amounts of SAM and dSAM (9). We have determined the course of the SAM decarboxylase reaction and have established the equimolar production of dSAM and CO2 from SAM by t...

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“…Bacteria, yeast, and animal cells do contain a well characterized SAM decarboxylase (23). However, in crude extracts, the usual test substrate, [1_-4CJS-adenosylmethionine may yield '4C02 by enzymatic reactions other than via a direct decarboxylation of SAM (19,24,25).…”

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S-Adenosylmethionine Decarboxylase and Spermidine Synthase from Chinese Cabbage

Yamanoha

Cohen²

1985

Plant Physiol.

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“…Such activity, however, has only been demonstrated in the soluble fraction of pig (Swiatek et al, 1973) and rat (Pietropaolo et al, 19712) liver extracts. Some indirect evidence supporting the existence, of adenosylmethionine cyclotransferase in the rat has also been reported (Edwards et al, 1977;Wilson et al, 1979).…”

Section: H3nmentioning

confidence: 85%

“…The pellet was thoroughly washed with appropriate buffer solution and then dissolved in buffer to regain the initial volume. Acetone-desiccated preparations were made from the soluble fractions essentially as described by Wilson et al (1979). Protein was determined in all preparations by the method of Lowry et al (1951), with bovine serum albumin as standard.…”

Section: Assaysmentioning

confidence: 99%

Catabolism and lability of S-adenosyl-l-methionine in rat liver extracts

Eloranta¹,

Kajander²

1984

Biochemical Journal

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The fate of S-adenosyl-L-methionine was studied in rat liver extracts by analysing the distribution of radioactivity from labelled adenosylmethionine in decomposition products, which were separated from each other by chromatographic and electrophoretic means. Marked non-enzymic degradation to adenine, pentosylmethionine, methylthioadenosine and homoserine was evident at pH 6.9-7.8. Enzymic cleavage to methylthioadenosine was stoichiometric with the accumulation of spermidine and could be totally prevented by inhibiting S-adenosyl-L-methionine decarboxylase. The results rule out the existence of adenosylmethionine cyclotransferase in rat liver and indicate that only two quantitatively significant enzymic processes are involved in hepatic adenosylmethionine degradation. Excluding nonenzymic decomposition, more than 99% of adenosylmethionine is demethylated and exclusively catabolized further by S-adenosyl-L-homocysteine hydrolase. Less than 1% of adenosylmethionine is decarboxylated and immediately utilized totally for polyamine biosynthesis.

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“…In a recent review, Williams-Ashman & Pegg (1981) pointed out that at the time of writing there was no convincing evidence for multiple forms of this enzyme. Sturman (1976a,b) had observed an activity liberating C02 from the carboxyl group of S-adenosylmethionine in detergent-treated rat liver particulate extracts, but subsequent investigations revealed that this activity was the result of a number of reactions degrading S-adenosylmethionine and releasing C02 from some of the products (Eloranta & Raina, 1978;Wilson et al, 1979;Pegg, 1979). Nevertheless, the possibility that different forms of the true S-adenosylmethionine decarboxylase exist had not been extensively tested, and recent experiments in this laboratory suggested that there may be differences between the enzymes present in liver and diaphragm or psoas muscle (Poso & Pegg,198la,b).…”

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Comparison of S-adenosylmethionine decarboxylases from rat liver and muscle

Pösö¹,

Pegg²

1982

Biochemistry

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S-Adenosylmethionine decarboxylase was purified to homogeneity from rat liver and from rat psoas. The major step involved affinity chromatography on methylglyoxal bis-(guanylhydrazone) linked to Sepharose. The muscle enzyme was more tightly retained to this absorbent, and the enzymes from the two sources could readily be separated by chromatography on this material. The psoas and liver enzymes could not be distinguished by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, both giving a single band corresponding to an Mr of 32 500, but were separated by electrophoresis under nondenaturing conditions and by isoelectric focusing (the isoelectric points were 5.3 for psoas and 5.7 for liver enzyme). The liver and psoas enzymes also differed in respect to Km for S-adenosylmethionine, the degree to which they were activated by putrescine, and their sensitivity to inhibition by methylglyoxal bis(guanylhydrazone) and related compounds. These results indicate that there are two forms of S-adenosylmethionine decarboxylase. The presence of a particular form could, therefore, be important both in the regulation of polyamine levels and also in the pharmacology involving inhibitors of polyamine synthesis.

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The decarboxylation of S-adenosylmethionine by detergent-treated extracts of rat liver

Cited by 17 publications

References 29 publications

S-Adenosylmethionine Decarboxylase and Spermidine Synthase from Chinese Cabbage

S-Adenosylmethionine Decarboxylase and Spermidine Synthase from Chinese Cabbage

Catabolism and lability of S-adenosyl-l-methionine in rat liver extracts

Comparison of S-adenosylmethionine decarboxylases from rat liver and muscle

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