Total Free Amino Acid Pool Research Articles

Species-specific metabolome changes during salinity downshift in sub-Arctic populations of Mytilus edulis and M. trossulus

The blue mussels Mytilus edulis and Mytilus trossulus are ecologically and economically important species distributed widely across the Northern Hemisphere. Understanding their behavioral and physiological disparities is crucial for assessing their ecological success and aquacultural value. The recent finding of non-native M. trossulus in the White Sea raises concerns regarding its potential competition with native M. edulis and its prospective spread in light of climate change and surface water freshening. We investigated the responses of M. edulis and M. trossulus to salinity variations by examining shell closure thresholds and tissue levels of 35 metabolic intermediates in mussels acclimated to different salinities (25, 16, and 10). The salinity threshold for valve closure was similar in both studied species, but M. trossulus consistently opened at lower salinities (by 0.2–0.7 practical salinity units) compared to M. edulis. Salinity-induced changes in metabolite levels were similar between the two species. Taurine emerged as the dominant osmolyte, comprising over 50% of the total free amino acid pool, with aspartate and glycine contributing 15–30%. Concentrations of taurine, glycine, and total free amino acids declined with decreasing salinity. Taurine to glycine ratios were higher in M. edulis and increased in both species with declining salinity. Acclimation salinity significantly influenced urea cycle intermediates and methionine sulfoxide content, a cellular biomarker of amino acid oxidation. Species-specific differences were observed in purine metabolism, with higher levels of GMP and AMP found in M. edulis. Likewise, aromatic amino acids and histidine levels were higher in M. edulis compared to M. trossulus. However, no evidence suggests superior adaptation of M. trossulus metabolism to hypoosmotic stress compared to M. edulis. Further research is necessary to elucidate the functional implications of subtle metabolic differences between these Mytilus congeners and their ecological consequences in changing marine environments.

Real-Time Infrared Spectroscopic Measurement of Natural Moisturizing Factor

Real-Time Infrared Spectroscopic Measurement of Natural Moisturizing Factor

Comparative freeze tolerance and physiological adaptations of three species of vertically distributed rocky intertidal gastropods from southeast Alaska

Tidal emersion temperatures are ameliorated on the coast of the continental United States because of the timing of low spring tides but spring low tides occur during the day in the summer and during the night in the winter in the inside passage north of Seattle. Extreme low air temperatures during the emersion of intertidal organisms at the northern intertidal sites render them vulnerable to freezing. To quantify the effects of freezing air temperatures on the supercooling point and freeze tolerance of Littorina sitkana from the upper intertidal, Nucella lima from the mid-intertidal, and Nucella lamellosa from the low intertidal, ambient temperatures were monitored with Hobo probes in two transects encompassing their intertidal distribution. To simulate the range of their emersion time the 2 and 5h supercooling and freeze tolerance of N. lamellosa, 5h supercooling and freeze tolerance of N. lima, and 5 and 10h freeze tolerance of L. sitkana were determined. Seasonal variability in the degree of hydration and free amino acid concentrations of these species was also determined. The number of days when emersion temperature fell below 0°C increased with intertidal height as did the number of hours per day when the emersion temperature was <0°C. The freeze tolerance temperature of these species increased directly with their intertidal distribution in 5hour emersion exposures and did not change with emersion temperature duration typical of their intertidal range. L. sitkana and N. lima were more tolerant of freezing in the winter than in the summer but there was no seasonal difference in the freeze tolerance of N. lamellosa. The supercooling point of the species varied directly with their intertidal distribution, did not vary seasonally and reduced the period of time during emersion when they were subject to freezing. Free amino acids contributed to the increased freeze tolerance of L. sitkana and N. lima in the winter. Although the total free amino acid pool of N. lamellosa was significantly higher by 30.6% in the winter than the summer, no single free amino acid was higher. There were significantly higher concentrations of total FAA (54.6% increase), taurine (22%) and glycine (2150%) in N. lima in the winter. There were significant increases of total FAA (27.6% increase), taurine and glycine in the winter compared to the summer in L. sitkana. These FAA are important compatible colligative osmolytes which enhance winter freeze tolerance.

Effects of Gibberellic Acid on Hemolymph-Free Amino Acids of Galleria mellonella (Lepidoptera: Pyralidae) and Endoparasitoid Pimpla turionellae (Hymenoptera: Ichneumonidae)

Abstract The impacts of the plant growth regulator, gibberellic acid (GA3) were investigated on hemolymph free amino acids (FAAs) of Galleria mellonella L. (Lepidoptera: Pyralidae) larvae and its endoparasitoid Pimpla turionellae L. (Hymenoptera: Ichneumonidae) reared on host treated with different doses (50–5,000 ppm) of GA3 in diet. High-performance liquid chromatographic analysis of the hemolymph revealed that out of the 20 amino acids detected, 18 FAAs were found in the hemolymph of treated and untreated host larvae, whereas 19 were present in that of parasitoid. The total pool of FAAs in host larvae after treatment by GA3 fluctuated among doses and the ratio of essential amino acids in the pool increased to reach 9.54% at 1,000 ppm. Parasitoid larval total FAA concentration exhibited an increase at all treatments. However, the ratio of essential amino acids in the pool decreased &amp;gt;50% at all doses except for 50 ppm. Dose-dependent variations in individual FAAs in larval hemolymph of both species were also detected. Tyrosine, methionine, isoleucine, lysine, and tryptophan generally occurred in lowest amount both in control and treated G. mellonella larvae. The amount of serine, asparagine, glycine, isoleucine, leucine, and phenylalanine displayed differences only among GA3 doses in treatments. Great variations in the amount of all amino acids occurred at most of the treatment doses in wasp larvae hemolymph. Our study indicated that application of GA3 resulted in different effects on the quantity of FAAs associated with energy metabolisms of the pest species and its natural enemy.

Seasonal changes of free amino acids and thermal hysteresis in overwintering heteropteran insect, Pyrrhocoris apterus

Overwintering adults of Pyrrhocoris apterus do not tolerate freezing of their body fluids and rely on a supercooling strategy and seasonal accumulation of polyols to survive at subzero body temperatures. We sampled the adults monthly in the field during the cold season 2008–2009 and found active thermal hysteresis factors (THFs) in hemolymph of winter-sampled adults. The hysteresis between the equilibrium melting and freezing points ranged from 0.18°C to 0.30°C. No signs of THFs activity were found in the autumn- and spring-sampled insects. The total free amino acid pool almost doubled during winter time. The sum concentrations of 27 free amino acids ranged between 35 and 40mM in whole body water and 40–45mM in hemolymph during December–February. Two amino acids, Pro and α-Ala most significantly contributed to the seasonal increase, while Gln showed the most dramatic seasonal decrease. Moderate levels of amino acid accumulation in overwintering P. apterus suggest that they are by-products of protein degradation and pentose pathway activity during the state of metabolic suppression imposed by diapause and low body temperature. Potential colligative effects of accumulated amino acids, extending the supercooling capacity of overwintering P. apterus, are negligible. Non-colligative effects require further study.

Variability of the total free amino acid (TFAA) pool in Mytilus galloprovincialis cultured on a raft system. Effect of body size

Variability of total free amino acid (TFAA) pool in Mytilus galloprovincialis was analysed following raft culture of growing mussels. With the aim to ensure the actual effect of animal’s size, a mussel population was sampled in laboratory covering the field size (15- to 60-mm shell length). TFAA showed a constant profile regardless size increase of individuals in both field and laboratory experiments. Environmental salinity and temperature varied within a relatively narrow range in the field (34–35 g L−1 and 14–19 °C, respectively). Despite the narrow variability of TFAA, significant differences were reported for the most representative amino acids. Specifically, taurine content significantly dropped with soft tissues increase in both field and laboratory experiments. Up to 40% of taurine drop in growing individuals was counterbalanced by the increase in alanine as main protein free amino acid (PFAA), whereas glycine showed high variability and inconsistency. PFAA increased linearly with the endogenous condition of individuals and were inversely correlated with protein content. In summary, TFAA pool of M. galloprovincialis remained unchanged with animal’s size, which might ensure optimal protein turnover rates during growth and establish a significant link between energetic status (condition) and PFAA, values that are equilibrated by a significant drop of the most abundant taurine.

Free amino acid composition in blood and muscle of the gobi Precottus glehni at the period of preparation and completion of hibernation

The freshwater fish gobi Preccottus glehni survives after wintering in ponds frozen in winter till the very bottom. In adaptation of poikilothermal animals to wintering at near-zero temperatures, an essential role is played by free amino acids; accumulation of a large amount of some particular acid at the period of preparation to the state of hibernation can indicate the protective role of this acid in the low-temperature adaptation. In the present work it has been shown that as soon as by the end of August, in the gobi muscle, the taurine concentration increases three times as compared with that in July, the taurine pool after this reaching 50% of the total pool of free amino acids in the muscle tissue. During December and after the 3-month hibernation in ice, it exceeds the April and July levels 8 and 4 times, respectively, and amounts to 50% of the total free amino acid pool for muscle and to 40% for blood. Several days prior to the beginning of winter hibernation under natural conditions, both in blood and in muscle, there is revealed disappearance or a sharp fall of concentration of essential amino acids. An essential peculiarity of the change in the free amino acid composition after hibernation was a significant rise of alanine concentration in muscle—3.5 times as compared with July and 1.4–1.8 times as compared with changes in December. The total free amino acid pool in muscle in December as compared with that in July increased almost 1.5 times (34.76 ± 1.12 μmol/g wet weight), while after hibernation—2 times. Peculiarities of taurine accumulation long before the beginning of winter cold allow suggesting that role of taurine consists in providing a possibility of existence of eurythermal fish at near-zero temperature.

O-glycosylhydrolases of embryos of the sea urchin Strongylocentrotus intermedius and effect of some natural substances on their biosynthesis

The fresh-water fish gobi Perccottus glehni survives after wintering in ponds frozen in winter until the very bottom. In adaptation of poikilothermal animals to wintering at nearzero temperatures, an essential role is played by free amino acids: accumulation of a high amount of some particular acid at the period of preparation to the state of hibernation can indicate its protector role in the low-temperature adaptation. In the present wok it has been shown that as early as by the end of August in the gobi muscle there occurs a 3-fold increase, as compared with that in July, of concentration of taurine whose pool after this accounts for 50 % of the total pool of the muscle tissue free amino acids. During December and after the 3-month hibernation in ice, it exceeded the April and July level 8 and 4 times, respectively, and amounted to 50 % of the total free amino acid pool for muscle and to 40 % for blood. Several days before the beginning of hibernation under natural conditions, both in blood and in muscle there was revealed disappearance of a sharp decrease of essential amino acid concentrations. An essential peculiarity of the change composition of free amino acids after hibernation was a significance increase of alanine concentration in muscle - 3.5 times as compared with that in July and 1.4-1.8 times as compared with December measurements. The total pool of free amino acids in muscle as compared with that in July rose in December almost 1.5 times (34.76 +/- 1.12 micromole/g wet weight), while after hibernation - 2 times. Peculiarities of the taurine accumulation before the onset of winter colds allow suggesting that the role taurine consists in provision of a possibility of survival of eurithermal fish at the nearzero temperatures.

Reducing Acrylamide Precursors in Raw Materials Derived from Wheat and Potato

A review of agronomic and genetic approaches as strategies for the mitigation of acrylamide risk in wheat and potato is presented. Acrylamide is formed through the Maillard reaction during high-temperature cooking, such as frying, roasting, or baking, and the main precursors are free asparagine and reducing sugars. In wheat flour, acrylamide formation is determined by asparagine levels and asparagine accumulation increases dramatically in response to sulfur deprivation and, to a much lesser extent, with nitrogen feeding. In potatoes, in which sugar concentrations are much lower, the relationships between acrylamide and its precursors are more complex. Much attention has been focused on reducing the levels of sugars in potatoes as a means of reducing acrylamide risk. However, the level of asparagine as a proportion of the total free amino acid pool has been shown to be a key parameter, indicating that when sugar levels are limiting, competition between asparagine and the other amino acids for participation in the Maillard reaction determines acrylamide formation. Genetic approaches to reducing acrylamide risk include the identification of cultivars and other germplasm in which free asparagine and/or sugar levels are low and the manipulation of genes involved in sugar and amino acid metabolism and signaling. These approaches are made more difficult by genotype/environment interactions that can result in a genotype being "good" in one environment but "poor" in another. Another important consideration is the effect that any change could have on flavor in the cooked product. Nevertheless, as both wheat and potato are regarded as of relatively high acrylamide risk compared with, for example, maize and rice, it is essential that changes are achieved that mitigate the problem.

Effect Of Supplementation With Hydrolyzed Whey Protein Enriched With Glutamine Dipeptide On Performance Of Triathletes

Glutamine is a popular dietary supplement consumed for purported ergogenic benefits. Glutamine is the most abundant amino acid found in skeletal muscle and plasma, and it comprises over 60% of the total free amino acid pool. In situations of stress, such as intense exercise, the concentration of glutamine in the blood is decreased. Glutamine supplementation has been reported to enhance protein synthesis as well as improve immune function. PURPOSE: The effect of hydrolyzed whey protein enriched with glutamine dipeptide (Gln) supplementation on performance of triathletes was investigated. METHODS: Nine elite triathletes performed two exhaustive exercise trials in one week interval. Thirty minutes before starting a treadmill exhaustive exercise the subjects ingested 50 g of maltodextrin (placebo) or 50 g of maltodextrin plus 4 tablets of 700 mg of hydrolyzed whey protein enriched with 175 mg of glutamine dipeptide dissolved in 250 mL water. RESULTS: During the test, there was no difference in heart rate (190 ± 9 HR/min) and subjective perception of effort when compared the athletes supplemented or not with Gln. There was no difference in the VO2 max due to the effect of Gln supplementation. On the other hand, the % VO2 max increased when compared Gln supplemented athletes (87.22 ± 4.47 %) with placebo group (79.33 ± 4,3 %). CONCLUSION: Hydrolyzed whey protein enriched with glutamine dipeptide supplementation increased the performance of triathletes during treadmill exhaustive exercise. Suported by FAPESP, CAPES, CnpQ

Changes in Free Amino Acids and Sugars in Potatoes Due to Sulfate Fertilization and the Effect on Acrylamide Formation

To examine how sulfur deprivation may affect acrylamide formation in cooked potatoes, three varieties of potato were grown under conditions of either severe sulfur deprivation or an adequate supply of sulfur. In all three varieties sulfur deprivation led to a decrease in acrylamide formation, even though the levels of sugars, which are acrylamide precursors, were higher in tubers of the sulfur-deprived plants. In one variety the concentration of free asparagine, the other precursor for acrylamide, was also higher. There was a very close correlation between the concentration of asparagine in the tubers expressed as a proportion of the total free amino acid pool and the formation of acrylamide upon cooking, whereas sugars were poorly correlated with acrylamide. In potatoes, where concentrations of sugars are usually limiting, competition between asparagine and other amino acids participating in the Maillard reaction may be a key determinant of the amount of acrylamide that is formed during processing.

Metabolic responses to cold in subterranean crustaceans

Changes in polyol, sugar and free amino acid (FAA) body contents were investigated in the aquatic, subterranean (i.e. hypogean) crustaceans Niphargus rhenorhodanensis and Niphargus virei and in a morphologically close aquatic, surface-dwelling (i.e. epigean) crustacean Gammarus fossarum acclimated to 12 degrees C, 3 degrees C and -2 degrees C. With decreasing temperature, G. fossarum significantly increased its alanine and glutamine levels, while trehalose body content was found to increase above control levels only at -2 degrees C. N. virei showed moderate increases of alanine and glycine, and no change in trehalose level was observed in this species. By contrast, N. rhenorhodanensis was the only species showing a significant rise in its total FAA pool, mainly explained by alanine, glycine, arginine and glutamine accumulations. This species also gradually increased its trehalose body content with decreasing temperature. Several cold-hardy ectotherms show metabolic responses to cold that are identical to those observed in N. rhenorhodanensis. A previous comparative study showed that the hypogean N. rhenorhodanensis exhibited a survival time (Lt50) at -2 degrees C that was 26.3 times and 2.6 times higher than the hypogean N. virei and the epigean G. fossarum, respectively. Thus, crustacean levels of FAA and trehalose were correlated with their respective cold tolerances. Such differences in metabolic responses to cold in both hypogean organisms were unexpected since they both live in thermally buffered biotopes. Considering the current distribution areas of the two subterranean crustaceans studied, we assume that the cold hardiness found in the hypogean N. rhenorhodanensis could be correlated with its biogeography history during the quaternary glaciations.

Effects of salinity on biochemical components of the mangrove, Aegiceras corniculatum

Salt induced biochemical changes were studied in hydroponically grown plants of a salt secrector mangrove, Aegiceras corniculatum (Myrsinaceae). Total Chl content decreased in 250 mM NaCl over the 30 d treatment period. The Chl a:b ratio remained unchanged in leaves, but carotenoids showed a 1.6-fold decrease. Total sugar content decreased to half in 250 mM NaCl and starch content increased by 174%. Leaf protein content decreased slightly and SDS-PAGE analysis showed nearly identical protein profiles in control and salt treated samples, which suggests that NaCl did not alter protein synthesis or proteolytic activity. The total free amino acid pool as well as the proline content decreased by 24 and 75% respectively in the leaves of 250 mM NaCl treated plants. The accumulation of polyphenols suggests a role as protective metabolites. The results show that the salt secreting mangrove A. corniculatum can be sustained and propagated under low salinity conditions. At high levels of salinity (∼250 mM) the plants become acclimated to salt in 1–2 weeks.

β-Alanine and other free amino acids during salinity adaptation of the polychaete Nereis japonica

The free amino acid pool was measured in the body wall muscle and in coelomic cells (eleocytes) of the polychaete Nereis japonica following adaptation to salinities between 6 and 44‰. β-Alanine and glycine were the major amino acids comprising 35–60% of the total free amino acid pool in the body wall. In eleocytes, glutamate and lysine in addition to β-alanine and glycine were the dominant free amino acids. In the body wall, the concentrations of β-alanine were closely correlated with the ambient salinity between 12 and 35‰. The concentrations of glycine rose initially but remained unchanged at concentrations above 26‰. In both body wall and eleocytes, the mean total primary amine concentrations were correlated with the ambient salinities between 12 and 35‰. The sum of amino acids determined by HPLC showed the same correlation in both tissues, but accounted only for 60–85% of the concentrations of total primary amines. The total protein content of the body wall was slightly higher at 44‰ compared to the lower salinities indicating dehydration of the tissues. Eleocytes swell at 6‰ and showed irregular amino acid concentrations indicating a loss of metabolic integrity.

Protein growth performance, amino acid utilisation and somatotropic axis responsiveness to fish meal replacement by plant protein sources in gilthead sea bream ( Sparus aurata)

Partial or total replacement of fish meal by a mixture of plant protein sources (corn gluten meal, wheat gluten, extruded peas, rapeseed meal) balanced with indispensable amino acids (IAA) was examined in juvenile gilthead sea bream ( Sparus aurata) over the course of a 12-week growth trial. A diet with fish meal (FM) as the sole protein source was compared to diets with 50%, 75% and 100% of replacement (PP50, PP75, PP100). Protein retention was improved with more plant protein supply, and just a slight decrease in the final weight gain was found in fish fed PP50 and PP75 diets. However, in the PP100 group, weight gain was depressed up to 30% mainly as the result of a marked reduction of feed intake. These fish also showed a lower fat gain along with a marked hypocholesterolemic effect. Dietary treatment did not alter the hepatic activity of amino acid catabolising enzymes (alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GDH)), although the size of the total muscle free amino acid (FAA) pool was increased by more plant protein supply. The activity of the somatotropic axis also varied among experimental groups, and the up-regulation of circulating growth hormone (GH) levels with a high plant protein supply followed the decrease in growth rates, plasma levels of insulin-like growth factor-I (IGF-I), and liver mRNA transcripts of IGF-I and GH receptors. This catabolic feature evidenced a liver desensitisation to the anabolic action of GH in the PP100 group, and to a lesser extent in the PP75 group. Taken together all these findings, up to 50–75% of fish meal replacement seems to be feasible with IAA supplementation, but further research is needed to fully identify the responsible factors for the depressed feed intake in order to achieve a full replacement in a fish species having high dietary protein requirements.

Variation in the free amino acid concentrations of the supralittoral rockpool copepod crustacean Tigriopus brevicornis during osmotic stress

Changes in the intracellular free amino acid (FAA) concentrations of Tigriopus brevicornis when subjected to hypoosmotic (5 psu), normal seawater (35 psu) and hyperosmotic (70 psu) conditions for a three day acclimation period were investigated. Proline, alanine and lysine were the major contributors to the intracellular FAA pool. Under hypoosmotic conditions, alanine was the dominant osmolyte with proline concentration at its lowest. This trend was reversed under hyperosmotic conditions. However, the total FAA pool was at its highest concentration under normal seawater conditions, with the total FAA concentrations being reduced during hypo- and hyper-osmotic conditions.

Protein kinase C and cAMP mediated regulation of taurine transport in human colon carcinoma cell lines (HT-29 & Caco-2).

Taurine is one of the most abundant free amino acids comprising 38% and 18% of the total free amino acid pool in human duodenal and colonic mucosa, respectively1. Recent observations have demonstrated that serum and intestinal taurine concentrations were lower in patients with cancer2, trauma3, surgery4 and critical illnesses5 compared to healthy controls. These results postulate the possibility that intestinal taurine absorption might be impaired in such stressed conditions. Taurine transport across the intestinal epithelium plays an important role in the regulation of taurine homeostasis in neonates and adults particularly under diverse stressed conditions6. The brush border membrane of intestinal mucosal cells express the Na+- and Cl--dependent taurine transporter (TAUT) responsible for the active absorption of taurine across the epithelium. TAUT activity in the intestinal epithelium is known to be regulated in response to changes in the availability of dietary sulfur amino acids6,7.

Study on the free amino acid levels in the hemolymph, gill, hepatopancreas and muscle of Penaeus monodon exposed to elevated ambient ammonia

Tiger shrimp Penaeus monodon following 24 h exposure to 0.002 (control), 0.072 and 0.718 mM ammonia were examined for the free amino acid (FAA), ammonia and urea levels in the hemolymph, gill, hepatopancreas and muscle. Control shrimps contained total FAA in hemolymph (1.19 μmol ml −1), gill (21.81 μmol g −1), hepatopancreas (100.81 μmol g −1) and muscle (239.54 μmol g −1). Glycine and arginine were the major contributors to the total FAA pool, and made up of 90% of the total FAA in the muscle of P. monodon. The total FAA level in the hemolymph increased directly with ambient ammonia, whereas the total FAA level in the hepatopancreas was inversely related to ambient ammonia. No significant difference of total FAA was observed in the gill and muscle among the shrimps in three treatments. Ammonia level increased by 160% in hemolymph, 105% in gill, 236% in hepatopancreas and 68% in muscle for the shrimps exposed to 0.718 mM ammonia. Urea and ornithine in the hepatopancreas increased by 107 and 1446%, whereas arginine level in the hepatopancreas decreased by 50% for the 0.718 mM ammonia-exposed shrimps. Decreases of arginine and other FAA with a concomitant increase of ornithine and urea level in the hepatopancreas indicated catabolism of FAA and ureogenesis. Increases of ammonia, urea, taurine, glutamine, proline, alanine, glycine and asparagine in the hemolymph revealed a intracellular osmoregulation for P. monodon under the stress of ambient ammonia at 0.718 mM.

Effect of regular training on the myocardial and plasma concentrations of taurine and alpha-amino acids in thoroughbred horses.

Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 +/- 1.2 mumol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 +/- 0.9 and 7.7 +/- 0.69 mumol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1 mumol/g wet weight (4.6 +/- 0.25 and 1.7 +/- 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 +/- 1.1 mumol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.

Betaine aldehyde dehydrogenase in sorghum.

The ability to synthesize and accumulate glycine betaine is wide-spread among angiosperms and is thought to contribute to salt and drought tolerance. In plants glycine betaine is synthesized by the two-step oxidation of choline via the intermediate betaine aldehyde, catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase (BADH). Two sorghum (Sorghum bicolor) cDNA clones, BADH1 and BADH15, putatively encoding betaine aldehyde dehydrogenase were isolated and characterized. BADH1 is a truncated cDNA of 1391 bp. BADH15 is a full-length cDNA clone, 1812 bp in length, predicted to encode a protein of 53.6 kD. The predicted amino acid sequences of BADH1 and BADH15 share significant homology with other plant BADHs. The effects of water deficit on BADH mRNA expression, leaf water relations, and glycine betaine accumulation were investigated in leaves of preflowering sorghum plants. BADH1 and BADH15 mRNA were both induced by water deficit and their expression coincided with the observed glycine betaine accumulation. During the course of 17 d, the leaf water potential in stressed sorghum plants reached -2.3 MPa. In response to water deficit, glycine betaine levels increased 26-fold and proline levels increased 108-fold. In severely stressed plants, proline accounted for > 60% of the total free amino acid pool. Accumulation of these compatible solutes significantly contributed to osmotic potential and allowed a maximal osmotic adjustment of 0.405 MPa.