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At least 19 recordsLinked to original sources
PubMed1978

Utilization of dietary sulfur compounds by fingerling channel catfish: L-methionine, DL-methionine, methionine hydroxy analogue, taurine and inorganic sulfate.

Sixteen isonitrogenous, isoenergetic diets were fed to fingerling channel catfish to study the efficacy of L-methionine, DL-methionine, methionine hydroxy analogue (OH-M), taurine and sodium sulfate. The basal diet contained casein and gelatin supplemented with crystalline L-amino acids to correspond to the amino acid pattern found in 24% crude protein from whole egg powder. The basal diet, containing 0.26% methionine was supplemented with graded levels of each of the sulfur sources on an isosulfurous basis. Growth and feed efficiency data indicate that channel catfish can utilize DL-methionine as effectively as L-methionine. OH-M was only about 26% as effective in promoting growth as L-methionine. No significant growth response was observed when taurine or inorganic sulfate was added to the basal diet.

Amino Acids↗
PubMed1976

Nitrogen retention in men fed isolated soybean protein supplemented with L-methionine, D-methionine, N-acetyl-L-methionine, or inorganic sulfate.

The ability of various sulfur-containing compounds to replace L-methionine (L-Met) was investigated by metabolic balance studies in man. N-acetyl-L-Methionine (AcMet), D-methionine (D-Met), and sodium sulfate (Na2SO4) were used to supplement a diet deficient in sulfur amino acids. The daily diet contained 4.5 g nitrogen (N) from isolated soybean protein (SB) and 4.5 g from glycine and alanine (9 g total N). SB diet was given alone or supplemented to six adult men for periods of 9 days after a standardization period with an equal N eggwhite diet, preceded by a 2-day zero N adaptation period. Supplements provided equivalent amounts of sulfur to that present in 420 ml L-Met, the amount added to SB to bring the total sulfur amino acid content to 900 mg/day. AcMet was as benfeficial as L-Met in improving N balance but D-Met was not as effective as L-Met. Difference between balances obtained with L-Met and Na2SO4 was not significant due to large variation in response to Na2SO4. While addition of D-Met to SB did not result in significantly greater N retention than unsupplemented SB, NA2SO4 addition did cause increased N retention.

Adult↗
PubMed1977

Effects of excess dietary l-methionine and N-acetyl-l-methionine on growing rats.

We have determined the effects of excessive dietary intakes of L-methionine and N-acetyl-L-methionine by measuring parameters which are known to be affected by excess methionine. Male Sprague-Dawley weanling rats were fed complete diets containing 10% protein supplied as isolated soybean protein and graded levels of supplemental L-methionine (from 0.30% to 5.0%) or equimolar levels of N-acetyl-L-methionine. The basal diet without supplemental methionine contained 0.15% methionine. Rats fed diets containing 0.3% supplemental L-methionine or the equivalent levels of supplemental N-acetyl-L-methionine grew best. Higher dietary levels of either L-methionine or N-acetyl-L-methionine caused progressive decreases in weight gain. However, L-methionine at 1.8% and above tended to more severely depress growth than did equivalent amounts of N-acetyl-L-methionine. L-Methionine at levels of 1.2% and above, or equivalent levels of N-acetyl-L-methionine caused comparable hypertrophy of the spleen and comparable increases in spleen iron levels. Hematocrits were not affected by either L-methionine or N-acetyl-L-methionine at the levels used in this experiment. We have concluded that N-acetyl-L-methionine is no more detrimental than L-methionine and is less detrimental at very high levels as evidenced by weight gain.

Animals↗
PubMed1975

Comparative metabolism of L-methionine and N-acetylated derivatives of methionine.

These experiments compared the metabolism of the N-acetylated derivatives of D- or L-methionine to that of L-methionine. Spargue-Dawley rats were orally or intraperitoneally dosed with N-[1-14C]acetyl-L-methionine, N-[1-14C]acetyl-D-methionine, or sodium [1-14C]acetate. 14CO2 was collected at intervals over 24 hours. In addition, groups of rats were orally dosed with either 35S-labeled N-acetyl-L-methionine or L-methionine. The animals were killed 3, 24, and 168 hours after dosing. Urine and feces were collected, and tissues were excised for 35S determinations. With either route of dosing, N-[1-14C]acetyl-L-methionine yielded the same amount of 14CO2 as sodium [1-14C]acetate over a 24-hour period. The acetate moiety of N-[1-14C]acetyl-D-methionine is not readily metabolized to 14CO2. Within each time period after dosing, the tissue distribution of 35S from 35S-labeled N-acetyl-L-methionine and L-methionine was similar. Protein specific activities for the two isotopes were also the same. After 168 hours, 30% of both isotopes of 35S appeared in the urine and feces, and the two isotopes were similarly distributed in the organic -S and inorganic -S fractions of urine. The studies show that L-methionine from N-acetyl-L-methionine is metabolically equivalent to free L-methionine. This conclusion is consistent with rat feeding studies showing that N-acetyl-L-methionine is nutritionally equivalent to L-methionine.

Acetates↗
PubMed1977

Transport and utilization of D-methionine and other methionine sources in Escherichia coli.

The transport and utilization of D-methionine was investigated in several strains of Escherichia coli K-12. Wild-type cells exhibit a single transport system with a Km of 1.16 muM. This activity exhibits a specificity similar to that of the uptake of L-methionine. The activity toward the D-isomer and the high-affinity uptake of L-methionine are lost in strains mutant in metD, along with the ability to utilize D-methionine as methionine source. Both activities respond identically to gene dosage of metD and are both restored in revertants or transductants. However, although L-methionine is a potent inhibitor of D-methionine uptake, D-methionine has little or no effect on the uptake of the L-isomer. No mutants altered in the uptake of only one of the two isomers were found in a screening. Regulation of both activities was similar in their response to the internal methionine pool, and some evidence was suggestive of partial repressive control of these activities. The evidence is most consistent with the role of the metD product as a common step for two methionine-specific uptake systems, but other gene products may represent the initial substrate binding sites. This system also appears to be involved in the uptake of N-acetyl methionine and methionine sulfoxide and methionine sulfoximine. The uptake of the keto analogue of methionine, alpha-keto-gamma-methiol butyrate, appears to be mediated by a separate system specific for alpha-keto straight-chain acids 5- to 6-carbon units in length.

Binding, Competitive↗
PubMed1976

Utilization of L-methionine sulfoxide, L-methionine sulfone and cysteic acid by the weanling rat.

Three experiments were conducted to test the ability of weanling rats to utilize the oxidized forms of the sulfur amino acids methionine and cysteine for growth. In the first two experiments, diets were fed which contained graded levels of methionine, methionine sulfoxide and methionine sulfone. The third experiment included a comparison of two dietary levels of cysteine and cysteic acid. The 2 week weight gain and food consumption data indicated that methionine sulfoxide was utilized for growth with only 60% of the efficiency of that achieved by rats fed methionine. Methionine sulfone was not utilized for growth. Analysis of plasma sulfur amino acids showed that the rat has a limited capacity to utilize methionine sulfoxide by effecting its reduction to methionine. Cysteic acid did not support weight gain. This amino acid appeared to be rapidly catabolized to taurine. It was concluded that methionine sulfone and cysteic acid cannot be utilized by the weanling rat. Methionine sulfoxide cannot fully meet the dietary requirement of the rat methionine because of its limited capacity to reduce this amino acid.

Amino Acids↗
PubMed1976

An evaluation of the L-methionine activity of the hydroxy analogue of methionine.

Three product forms of methionine hydroxy analogue were prepared for biological evaluation of their L-methionine activity for broiler strain chickens (Vantress x Arbor Acres). Two samples of the acid of the analogue HA-50, LMA-70 and one sample of a commercial grade (90%) MHA were standarized by gas liquid chromatography to contain a known amount of L-methionine activity as the free analogue acid. Each product form was tested in a separate experiment. The experimental chickens were fed a practical corn-soybean meal basal diet for the first seven days of the test. A semi-purified diet composed primarily of cerelose, isolated soybean protein and soybean meal was used for the remainder of the experimental period. HA-50 and the commercial form of the hydroxy analogue were formulated to contain 50% L-methionine activity. Hence, they were added to the diets at 0.1 and 0.2% and compared to the L-methionine standard which was added to levels of 0.05, 0.1 and 0.15%. LMA-70 was formulated to contain 70% L-methionine activity and was added to the experimental diets at 0.07 and 0.14% and compared to the L-methionine standard at the same levels used in the other experiments. Statistical analysis of four-week data revealed no difference between the biological response of L-methionine and the three forms of the analogue when tested at comparable L-methionine activity levels. The biological of the analogue products was in good agreement with the L-methionine activity determined by gas liquid chromatography.

Animal Feed↗
PubMed1976

Carboxymethylation of methionine residues in bovine pituitary luteinizing hormone and its subunits. Location of specifically modified methionine residues.

Bovine lutropin (luteinizing hormone) was carboxymethylated at pH3.0 for 12 h at 37 degrees C with iodoacetic acid for specific modification of methionine residues. To facilitate the location of preferentially modified methionine residues, iodoE114C]acetic acid was added as tracer. The alpha and beta subunits of bovine lutropin were carboxymethylated with a 2- or 5-fold molar excess of iodoacetic acid either in the presence or absence of their counterpart subunits. The modified subunits were separated and isolated by counter-current distribution followed by gel filtration on Sephadex G-100. To locate the modified methiones, the isolated alpha or beta chain was reduced. S-carboxymethylated and subjected to tryptic hydrolysis. The tryptic peptides were fractionated by gel filtration on Bio-Gel P-10. From analyses of the purified 14C-labelled tryptic peptides, it was observed that methionine-8 and -33 in bovine lutropin alpha chain and methionine-52 in the beta chain were preferentially modified. Similar results were obtained when isolated alpha and beta subunits were individually carboxymethylated in the absence of their counterpart subunit under identical conditions. The fact that a recombinant of native human lutropin alpha chain, in which a valine residue is present in the position corresponding to methionine-8 of bovine lutropin alpha chain, and carboxymethylated bovine lutropin beta chain regenerated a substantial amount of receptor-site-binding activity indicated that methionine-8 in bovine alpha chain was biologically not essential. These studies showed clearly that both methionine-33 in the alpha chain and methionine-52 in the beta subunit were involved for optimum binding between bovine lutropin and its receptors for expression of hormonal activity.

Amino Acid Sequence↗
PubMed1975

The role of methionine transport-defective mutations in resistance to methionine sulphoximine in Salmonella typhimurium.

Two classes of Salmonella typhimurium mutants resistant to inhibitory methionine analogues and defective in methionine transport have been examined. A mutant of the first class, resistant to alpha-methylmethionine, was shown by conjugation analysis to possess a single mutation in the metP gene which specifies a methionine transport system. Mutants of the second class, resistant to alpha-methylmethionine and methionine sulphoximine, possess two mutations. One is in the metP gene, which accounts for resistance to alpha-methylmethionine, and the other is in a gene designated glnP which results in reduced L-glutamine transport. Both of these mutations are required for resistance to methionine sulphoximine. A transduction analysis of three metP mutations was performed, based on the fact that they prevent growth of methionine-requiring strains on D-methionine. Two of the mutants are closely linked and therefore probably in the same gene, whereas the third mutant might be in a different gene.

Biological Transport↗
PubMed1975

Methionine-and S-adenosyl methionine-mediated repression in a methionyl-transfer ribonucleic-acid synthetase mutant of Saccharomyces cerevisiae.

A Saccharomyces cerevisiae mutant strain unable to grow at 38 C and bearing a modified methionyl-transfer ribonucleic acid (tRNA) synthetase has been studied. It has been shown that, in this mutant, the percentage of tRNAmet charged in vivo paralleled the degree of repressibility of methionine biosynthetic enzymes by exogenous methionine. On the contrary, the repression mediated by exogenous S-adenosylmethionine does not correlate with complete acylation of tRNAmet. Althought McLaughlin and Hartwell reported previously that the thermosensitivity and the defect in the methionyl-tRNA synthetase were due to the same genetic lesion (1969), no diffenence could be found in the methionyl-tRNA synthetase activity or in the pattern of repressibility of methionine biosynthetic pathway after growth at the premissive and at a semipermissive temperature. It appears that the mutant also exhibits some other modified characters that render unlikely the existence of only one genetic lesion in this strain. A genetic study of this mutant was undertaken which led to the conclusion that the thermosensitivity and the other defects are not related to the methionyl-tRNA synthetase modification. It was shown that the modified repressibility of methionine biosynthetic enzymes by methionine and the lack of acylation of tRNAmet in vivo follow the methionyl-tRNA synthetase modification. These results are in favor of the idea that methionyl-tRNAmet, more likely than methionine, is implicated in the regulation of the biosynthesis of methionine.

Amino Acyl-tRNA Synthetases↗
PubMed1978

Methionine-cystine interrelations in chicks fed diets containing suboptimal levels of methionine.

Studies were conducted with chicks on the interrelationship between cystine and methionine in either crystalline amino acid or wheat-peanut meal diets containing suboptimal levels of these two amino acids. The crystalline amino acid basal diet contained 0.2% DL-menthionine and 0.2% L-cystine whereas the wheat-peanut meal diet contained 0.2% methionine and 0.26% cystine. Marked improvements in weight gain and feed efficiency were observed when these diets were supplemented with 0.2 to 0.6% DL-methionine. When similar levels of L-cystine were added to the basal diets containing 0.2% methionine, chick growth was depressed. When the diets contained 0.4% methionine, the growth depressing effect of cystine was not observed. These results point to the existence of an antagonism of cystine on methionine utilization when the dietary level of methionine is suboptimal.

Amino Acids, Sulfur↗
PubMed1976

Facile alkylation of methionine by benzyl bromide and demonstration of fumarase inactivation accompanied by alkylation of a methionine residue.

Benzyl bromide is a selective alkylator of sulfur nucleophiles including methionine and cysteine. Only the mercaptide ion is a more efficient nucleophile than is the sulfur ether of methionine. Alkylation rates relative to methionine are 200: less than or equal to 0.03: less than or equal to 0.03: less than or equal to 0.02 for GS-, histidine, tryptophan, and GSH, respectively. Alkylation of methionine by benzyl bromide is more than 50 times faster than alkylation by iodoacetate. Fumarase is readily inactivated by exposure to benzyl bromide at pH 6.6 to 6.8 accompanied by alkylation of close to 1 methionine residue/subunit. Fumarase fully inactivated by exposure to benzyl bromide shows no detected alkylation of amino acid residues other than methionine. The rate of inactivation of fumarase by benzyl bromide is decreased about 4-fold by the presence of excess substrates. Denaturation of fumarase in 6 M urea at pH 6.5 exposes additional methionine as well as cysteine residues to alkylation.

Animals↗
PubMed1976

Methionine degradation by Pseudomonas fluorescens UK1 and its methionine-utilizing mutant.

Pseudomonas fluorescens UK1, and a mutant derived from it that can use methionine as its sole source of carbon and nitrogen, were used to study methionine degradation. Radioactive 2-oxomethionine, 2-oxobutyric acid and carbon dioxide comprised 95% of [I-14C]methionine consumed by the mutant. Demethiolating activity was detected in both strains when they were grown with methionine. The ability to grow on methionine depended on the decarboxylation of 2-oxobutyric acid derived from it. This decarboxylating activity was lost if the growth media contained an additional carbon source. No evidence was obtained for the operation of the cystathionine pathway.

Butyrates↗
PubMed1979

Reduction of methionine sulfoxide to methionine by Escherichia coli.

L-Methionine-dl-sulfoxide can support the growth of an Escherichia coli methionine auxotroph, suggesting the presence of an enzyme(s) capable of reducing the sulfoxide to methionine. This was verified by showing that a cell-free extract of E. coli catalyzes the conversion of methionine sulfoxide to methionine. This reaction required reduced nicotinamide adenine dinucleotide phosphate and a generating system for this compound. The specific activity of the enzyme increased during logarithmic growth and was maximal when the culture attained a density of about 10(9) cells per ml.

Escherichia coli↗
PubMed1975

Adverse effect of excess methionine or methionine hydroxy analog on feed consumption in cattle.

The toxicity of DL-methionine and methionine hydroxy analog infused into the rumen or abomasum was gauged by relative feed consumption. A continuous intraruminal infustion of at least 3 days' duration of DL-methionine equalent to about 2.5% or more of dietary dry matter intake was required to reach a toxic amount. This was approximately four times the amount necessary when it was infused into the abomasum. Methionine hydroxy analog equalent to about 1% or more of dietary dry matter intake was toxic when infused into either rumen or abomasum. This is in large excess of suggested amounts of analog supplementation. Reduced palatability is likely to occur in advance of reduced intake due to toxicity.

Abomasum↗
PubMed1977

The relative efficiency of DL-methionine and methionine hydroxy analogue-calcium (MHAC) in the diet of turkey poults.

Two experiments were conducted to evaluate the relative efficiency of methionine and methionine hydroxy analogue-calcium (MHAC) in the diet of turkey poults. A corn-soybean diet containing 25% protein and 2583 kilocalories of metabolizable energy per kilogram was utilized. Five experimental diets were fed: basal, 0.04 and 0.08% supplemental DL-methionine and 0.04 and 0.08% supplemental MHAC. In both experiments eight pens of seven poults were fed each experimental diet. This resulted in a total of 16 replicate pens receiving each diet. Body weight and feed efficiency were measured at four weeks of age. The MHAC, on a weight basis, was found to have 82.4 and 82.8% activity of DL-methionine based on body weight and feed efficiency, respectively.

Animal Feed↗