Developmental changes in the activities of enzymes related to methyl group metabolism in sheep tissues

Xue, Gang-Ping; Snoswell, Alan M.

doi:10.1016/0305-0491(86)90340-8

Cited by 25 publications

(26 citation statements)

References 21 publications

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“…BHMT is very abundant in the liver in most species, representing 0.6-1.6% of the total protein [8,22,26], whereas in the kidney, the activity observed is lower for humans and pigs and very low for rats [22,27]. In contrast, in sheep, the highest levels of activity correspond to the pancreas [28], such a distribution being attributed to the low oxidation of choline observed in these animals that could be an adaptation mechanism to the reduced levels of this metabolite in ruminant diets. BHMT has also been detected in the lens of Rhesus monkeys (Macaca mulatta), where it represents 0.5-10% of the total protein [29].…”

Section: Bhmt Distributionmentioning

confidence: 61%

Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?

Pajares

Pérez‐Sala

2006

Cell. Mol. Life Sci.

174

108

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Betaine homocysteine methyltransferase (BHMT), a Zn(2+)-dependent thiolmethyltransferase, contributes to the regulation of homocysteine levels, increases in which are considered a risk factor for cardiovascular diseases. Most plasma homocysteine is generated through the liver methionine cycle, in which BHMT metabolizes approximately 25% of this non-protein amino acid. This process allows recovery of one of the three methylation equivalents used in phosphatidylcholine synthesis through transmethylation, a major homocysteine-producing pathway. Although BHMT has been known for over 40 years, the difficulties encountered in its isolation precluded detailed studies until very recently. Thus, the last 10 years, since the sequence became available, have yielded extensive structural and functional data. Moreover, recent findings offer clues for potential new functions for BHMT. The purpose of this review is to provide an integrated view of the knowledge available on BHMT, and to analyze its putative roles in other processes through interactions uncover to date.

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Section: Bhmt Distributionmentioning

confidence: 61%

Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?

Pajares

Pérez‐Sala

2006

Cell. Mol. Life Sci.

174

108

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“…Xue and Snoswell (1985) compared enzyme activities involved in methionine metabolism in sheep (ruminants) and rats (nonruminants), and they demonstrated that sheep had relatively low hepatic BHMT activity and high hepatic 5-MHMT activity when compared to rats. Xue and Snoswell (1986) also compared enzyme activities in preruminant lambs vs mature sheep and observed a decrease in BHMT and a compensatory increase in 5-MHMT when lambs reached a ruminant state.…”

Section: Methodsmentioning

confidence: 99%

Methionine as a methyl group donor in growing cattle

Löest

Titgemeyer

Metre

et al. 2002

Journal of Animal Science

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Holstein steers were used in two 5 x 5 Latin square experiments to evaluate the sparing of methionine by alternative sources of methyl groups (betaine and choline). Steers were housed in metabolism crates and limit-fed a soybean hull-based diet high in rumen degradable protein. To increase energy supply, ruminal infusions of volatile fatty acids and abomasal infusions of glucose were provided. An amino acid mixture, limiting in methionine, was infused abomasally to ensure that nonsulfur amino acids did not limit protein synthesis. Treatments for Exp. 1 were abomasal infusion of 1) water, 2) 2 g/d L-methionine, 3) 1.7 g/d L-cysteine, 4) 1.6 g/d betaine, and 5) 1.7 g/d L-cysteine + 1.6 g/d betaine. Treatments for Exp. 2 were abomasal infusion of 1) water, 2) 2 g/d L-methionine, 3) 8 g/d betaine, 4) 16 g/d betaine, and 5) 8 g/d choline. In both experiments, nitrogen retention increased in response to methionine (P < 0.05), demonstrating a deficiency of sulfur amino acids. Responses to cysteine, betaine, and choline were all small and not significant. The lack of response to cysteine indicates that the response to methionine was not due to transsulfuration to cysteine or that cysteine supply did not alter the flux of methionine through transsulfuration. The lack of response to betaine suggests that the steers' needs for methyl groups were met by the dietary conditions or that betaine was relatively inefficient in increasing the remethylation of homocysteine to methionine and, thereby, reducing the synthesis of cysteine from homocysteine. Under our experimental conditions, responses to methionine were likely due to a correction of a deficiency of methionine per se rather than of methyl group donors.

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“…This situation has been demonstrated in adult and in particular lactating sheep (Henderson et al 1983;Robinson et al 1984;Xue & Snoswell, 1986a,b;Snoswell & Xue, 1987) (Table 2). This state is probably an adaptation to the low availability of dietary choline in adult ruminants (Xue & Snoswell, 1986a).…”

Section: Choline As Methyl Donormentioning

confidence: 98%

“…The increasing activities of liver choline oxidase and betaine-HCy methyltransferase in preruminant lambs are probably related to the abundance of choline-containing compounds in the milk (Xue & Snoswell, 1986a). Thus, the availability of choline and its metabolite betaine appear to influence the conversion or recycling of the HCy moiety of Met, through betaine-HCy methyltransferase activity (Stipanuk, 1986).…”

Section: Choline As Methyl Donormentioning

confidence: 99%

Comparative mammalian choline metabolism with emphasis on the high-yielding dairy cow

2002

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The present review examines the importance of choline in dairy cow nutrition. Choline is an essential nutrient for mammals when excess methionine and folate are not available in the diet. The requirement for choline can be met by dietary choline and by transmethylation reactions. Two types of functions for choline are known: functions of choline per se; functions as a methyl donor. The two principal methyl donors in animal metabolism are betaine, a metabolite of choline, and S-adenosyl-methionine, a metabolite of methionine. Choline and methionine are interchangeable with regard to their methyl group-furnishing functions. In adult ruminants, choline is extensively degraded in the rumen; for this reason dietary choline contributes insignificantly to the choline body pool and methyl group metabolism is generally conservative with a relatively low rate of methyl catabolism and an elevated rate of de novo synthesis of methyl groups via the tetrahydrofolate system. In dairy ruminants, the dietary availability of choline is still low, but the output of methylated compounds in milk is high, and precursors from the tetrahydrofolate pathway are limiting, especially at the onset of lactation. Therefore choline may be a limiting nutrient for milk production in high-yielding dairy cows.

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Developmental changes in the activities of enzymes related to methyl group metabolism in sheep tissues

Cited by 25 publications

References 21 publications

Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?

Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?

Methionine as a methyl group donor in growing cattle

Comparative mammalian choline metabolism with emphasis on the high-yielding dairy cow

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