scholarly journals Cooperation between Lactococcus lactis and Nonstarter Lactobacilli in the Formation of Cheese Aroma from Amino Acids

2003 ◽  
Vol 69 (2) ◽  
pp. 734-739 ◽  
Author(s):  
Agnieszka Kieronczyk ◽  
Siv Skeie ◽  
Thor Langsrud ◽  
Mireille Yvon
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Lactococcus Lactis ◽  
Cheese Flavor ◽  
Major Process ◽  
Flavor Development ◽  
Cheese Aroma

ABSTRACT In Gouda and Cheddar type cheeses the amino acid conversion to aroma compounds, which is a major process for aroma formation, is essentially due to lactic acid bacteria (LAB). In order to evaluate the respective role of starter and nonstarter LAB and their interactions in cheese flavor formation, we compared the catabolism of phenylalanine, leucine, and methionine by single strains and strain mixtures of Lactococcus lactis subsp. cremoris NCDO763 and three mesophilic lactobacilli. Amino acid catabolism was studied in vitro at pH 5.5, by using radiolabeled amino acids as tracers. In the presence of α-ketoglutarate, which is essential for amino acid transamination, the lactobacillus strains degraded less amino acids than L. lactis subsp. cremoris NCDO763, and produced mainly nonaromatic metabolites. L. lactis subsp. cremoris NCDO763 produced mainly the carboxylic acids, which are important compounds for cheese aroma. However, in the reaction mixture containing glutamate, only two lactobacillus strains degraded amino acids significantly. This was due to their glutamate dehydrogenase (GDH) activity, which produced α-ketoglutarate from glutamate. The combination of each of the GDH-positive lactobacilli with L. lactis subsp. cremoris NCDO763 had a beneficial effect on the aroma formation. Lactobacilli initiated the conversion of amino acids by transforming them mainly to keto and hydroxy acids, which subsequently were converted to carboxylic acids by the Lactococcus strain. Therefore, we think that such cooperation between starter L. lactis and GDH-positive lactobacilli can stimulate flavor development in cheese.

Amino Acid Transporter X Is Required for Hematopoietic Stem Cell Maintenance through Regulating Specific Amino Acids Level

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1166-1166 ◽  
Author(s):  
Zhenrui Li ◽  
Keiyo Takubo ◽  
Pengxu Qian ◽  
Toshio Suda ◽  
Linheng Li
Keyword(s):  
Amino Acids ◽  
Stem Cell ◽  
Amino Acid ◽  
Acid Metabolism ◽  
Hematopoietic Stem ◽  
Cell Pool ◽  
Stem Cell Pool

Abstract Hematopoietic stem cells (HSCs) maintenance is required to preserve stem cell pool and compensate the dynamic loss of blood cells. Previous studies of HSCs maintenance mainly focus on the quiescent versus active state of HSCs and accumulated evidence indicates that metabolism plays a critical role in coordinating divergent stem cell states. While recent reports largely emphasized the role of catabolic glycolysis on long-term (LT) HSC maintenance, we found that free amino acids are enriched in primitive stem cell by ~1.5 fold. Given that amino acid metabolism in HSCs is largely unknown, we first cultured bone marrow (BM) cells with individual amino acid deprived medium to study the function of individual amino acids on HSCs in vitro. Surprisingly, we found that specific amino acids, including valine, methionine and threonine (VMT), are essential for maintaining primitive HSCs, as removing them (VMT) individually from media dramatically reduced primitive HSC number by over 95%. Thus, we hypothesize that specific amino acids are critical for preserving the stem cell pool and maintaining their function. To test it, we transplanted equal number of cells cultured with complete or individual VMT deprived media into lethally irradiated recipient mice and found VMT deprivation in vitro impaired stem cell repopulation ability. We also identified the amino acid transporter X (AATX) that is specifically expressed in HSCs and maintain VMT levels within the cell. Furthermore, inhibition of AATX reduced LT-HSC (LSK CD34- Flk2-) number in vivo. BM transplantation indicated that AATX inhibition impaired stem cell long-term reconstitution ability by over 2 fold. Our studies uncovered a role of amino acid metabolism in HSC maintenance and discovered the underlying molecular mechanism related to the amino acid transport. This finding may impact clinical treatment of blood disorders including leukemia. Disclosures No relevant conflicts of interest to declare.

The Contribution of Caseins to the Amino Acid Supply for Lactococcus lactis Depends on the Type of Cell Envelope Proteinase

1998 ◽  
Vol 64 (6) ◽  
pp. 1991-1996 ◽  
Author(s):  
Benedicte Flambard ◽  
Sandra Helinck ◽  
Jean Richard ◽  
Vincent Juillard
Keyword(s):  
Amino Acids ◽  
Growth Rate ◽  
Amino Acid ◽  
Lactococcus Lactis ◽  
Cell Envelope ◽  
Essential Amino Acids ◽  
Genetically Engineered ◽  
Amino Acid Requirements ◽  
Rate Limiting

ABSTRACT The ability of caseins to fulfill the amino acid requirements ofLactococcus lactis for growth was studied as a function of the type of cell envelope proteinase (PI versus PIII type). Two genetically engineered strains of L. lactis that differed only in the type of proteinase were grown in chemically defined media containing αs1-, β-, and κ-caseins (alone or in combination) as the sources of amino acids. Casein utilization resulted in limitation of the growth rate, and the extent of this limitation depended on the type of casein and proteinase. Adding different mixtures of essential amino acids to the growth medium made it possible to identify the nature of the limitation. This procedure also made it possible to identify the amino acid deficiency which was growth rate limiting for L. lactis in milk (S. Helinck, J. Richard, and V. Juillard, Appl. Environ. Microbiol. 63:2124–2130, 1997) as a function of the type of proteinase. Our results were compared with results from previous in vitro experiments in which casein degradation by purified proteinases was examined. The results were in agreement only in the case of the PI-type proteinase. Therefore, our results bring into question the validity of the in vitro approach to identification of casein-derived peptides released by a PIII-type proteinase.

scholarly journals Mutational Scan of the Human Immunodeficiency Virus Type 2 Integrase Protein

1998 ◽  
Vol 72 (5) ◽  
pp. 3916-3924 ◽  
Author(s):  
Fusinita M. I. van den Ent ◽  
Arnold Vos ◽  
Ronald H. A. Plasterk
Keyword(s):  
Amino Acids ◽  
Human Immunodeficiency Virus ◽  
Amino Acid ◽  
Cleavage Reaction ◽  
Viral Dna ◽  
Dna Integration ◽  
Immunodeficiency Virus

ABSTRACT Retroviral integrase (IN) cleaves linear viral DNA specifically near the ends of the DNA (cleavage reaction) and subsequently couples the processed ends to phosphates in the target DNA (integration reaction). In vitro, IN catalyzes the disintegration reaction, which is the reverse of the integration reaction. Ideally, we would like to test the role of each amino acid in the IN protein. We mutagenized human immunodeficiency virus type 2 IN in a random way using PCR mutagenesis and generated a set of mutants in which 35% of all residues were substituted. Mutant proteins were tested for in vitro activity, e.g., site-specific cleavage of viral DNA, integration, and disintegration. Changes in 61 of the 90 proteins investigated showed no phenotypic effect. Substitutions that changed the choice of nucleophile in the cleavage reaction were found. These clustered around the active-site residues Asp-116 and Glu-152. We also found alterations of amino acids that affected cleavage and integration differentially. In addition, we analyzed the disintegration activity of the proteins and found substitutions of amino acids close to the dimer interface that enhanced intermolecular disintegration activity, whereas other catalytic activities were present at wild-type levels. This study shows the feasibility of investigating the role of virtually any amino acid in a protein the size of IN.

scholarly journals SUN-266 Protein Induced Pancreatic Hormone Secretion Is Modulated by Vagal CaSR

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Mariana Norton ◽  
Simon C Cork ◽  
Aldara Martin Alonso ◽  
Anna G Roberts ◽  
Yateen S Patel ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hormone Secretion ◽  
Sensory Information ◽  
Glucagon Secretion ◽  
Vagal Afferents ◽  
Acid Uptake

Abstract The existence of a vago-vagal entero-pancreatic pathway, where sensory information from the gut can signal via vagal afferents to the brain to mediate changes in pancreatic function, has been recognised for over a century, and investigated extensively with regards to pancreatic exocrine secretions. However, the role of such pathways in pancreatic endocrine secretions has received less attention. The secretion of insulin and glucagon in response to protein and amino acids is conserved across species. This effect is thought to promote amino acid uptake into tissues without concomitant hypoglycaemia. We found that the essential amino acid L-Phenylalanine potently stimulates glucagon secretion, even when administered directly into the gut at small doses unlikely to significantly raise systematic levels. Administration of L-Phenylalanine also increased neuronal activation in the rat and mouse dorsal vagal complex, the central nervous system region directly innervated by vagal afferents. L-Phenylalanine modulates the activity of the calcium sensing receptor (CaSR), a nutrient sensor more commonly known for its role in calcium homeostasis, but which is thought to also act as a sensor of aromatic amino acids. Interestingly, the CaSR is one of the few nutrient sensors expressed in vagal afferents and in vitro calcium imaging revealed CaSR synthetic agonists activate subpopulations of vagal afferents. The role of CaSR in vivo was investigated further by selectively knocking down the CaSR in vagal afferents. Briefly, CaSR floxed mice were bilaterally injected directly into the nodose ganglion, where the cell bodies of vagal afferents are located, with a cre expressing adeno-associated virus. CaSR knockdown did not interfere with normal food intake, nor the vagal-dependent anorectic effects of cholecystokinin, or of L-Phenylalanine. However, it did blunt protein-induced glucagon secretion, suggesting involvement of the CaSR in the vagus nerve in protein sensing and glucose homeostasis. Future studies are required to determine the importance of vagal CaSR in protein induced pancreatic endocrine secretions, and the possibility of exploiting this circuit to develop new anti-diabetic therapies.

Incorporation of C14-amino acids into protein of isolated diaphragms: role of the adrenal steroids

1959 ◽  
Vol 197 (5) ◽  
pp. 1089-1092 ◽  
Author(s):  
Ira G. Wool ◽  
Edward I. Weinshelbaum
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Muscle Protein ◽  
Percentage Increase ◽  
Adrenal Steroids ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
Adrenalectomized Rats

The incorporation of C14-amino acids into a protein fraction of diaphragms incubated in vitro was measured. Adrenalectomy led to an increase in amino acid incorporation into protein. Cortisone (0.3 mg/day) administered to adrenalectomized rats tended to restore incorporation to normal; desoxycorticosterone (0.06 mg/day) was without effect. Larger doses of cortisone (1 or 2 mg/day) produced a marked reduction in amino acid incorporation into diaphragms from both normal and adrenalectomized rats. Fasting reduced histidine incorporation into muscle protein whether the donor rat was normal or adrenalectomized. Phenylalanine-3-C14 incorporation into diaphragm protein was measured at several phenylalanine concentrations. Despite large (100-fold) changes in the phenylalanine pool size the percentage increase in C14 incorporation after adrenalectomy was similar.

Studies on Synergism between Glucose and Amino Acids with Respect to Insulin Release in vitro

1980 ◽  
Vol 35 (1-2) ◽  
pp. 72-75 ◽  
Author(s):  
Qamar Khalid ◽  
M. Ataur Rahman
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Insulin Release ◽  
Direct Effects ◽  
Isolated Rat Islets ◽  
Effect Of Glucose ◽  
Stimulate Insulin Release

Abstract The mutual enhancement of the effect of insulin release by glucose and amino acids is not clearly understood. Present in vitro studies with isolated rat islets were undertaken to elaborate the role of amino acids on insulin release, particularly their interaction with glucose as well as among each other, which has been reported to lead to synergism in the hum an subjects.In the presence of 8.3 mм glucose, both arginine, as well as, leucine potentiated the effect of glucose which increased progressively with the increasing concentrations of the amino acid. This effect of arginine was not synergistic in nature because arginine did not stimulate insulin release in the absence of glucose.The effect of glucose and leucine was found to be additive and not synergistic.No synergism was exhibited by any of the amino acid pairs tested in the present study. Thus both phenylalanine and lysine did not potentiate the effect of either arginine or leucine. Arginine showed a mild, but significant potentiating effect on leucine-stimulated insulin release.It is suggested that synergism between glucose and amino acids and between certain amino acid pairs reported in m an may not be due to the direct effects of these stimuli on the beta cells, but some other factors in vivo may be involved.

The role of methionine and cystine in the growth and viability of secondary hair follicles of the Cashmere goat in vitro

1996 ◽  
Vol 1996 ◽  
pp. 175-175
Author(s):  
M. Souri ◽  
H. Galbraith ◽  
J.R. Scaife
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hair Follicle ◽  
Hair Follicles ◽  
Monomeric Form ◽  
Cashmere Goat ◽  
Heterogenous System ◽  
Hair Fibre

A supply of sulphur-containing amino acids is essential for the growth of hair fibre in animals.The main sulphur-containing amino acid quantitatively required for the synthesis of fibre protein is cystine or its monomeric form cysteine,which may be absorbed from the digestive tract or converted from methionine via the transulphuration pathway.The predominant sites of the transulphuration pathway in ruminants are the liver (Radcliffe and Egan,1978)and the heterogenous system in the skin (Downes et al,1964).The aims of the study were to determine the importance of the supply of cystine and methionine for the growth and viability of the cashmere secondary hair follicle in vitro and to investigate whether cystine could successfully be replaced by methionine in this homogenous system.

The acute transient polymorphic psychosis: a biochemical subtype of the cycloid psychosis

2003 ◽  
Vol 15 (1) ◽  
pp. 38-43 ◽  
Author(s):  
L Pepplinkhuizen ◽  
F M M A van der Heijden ◽  
S Tuinier ◽  
W M A Verhoeven ◽  
D Fekkes
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Psychotic Disorders ◽  
Acid Metabolism ◽  
Plasma Concentrations ◽  
One Carbon Metabolism ◽  
The One

Background:The pathogenesis of atypical psychoses, in particularly those characterized by polymorphic psychopathology, is hypothesized to be related to disturbances in amino acid metabolism.Objective:In the present study, the role of the amino acid serine was investigated in patients with acute transient polymorphic psychosis.Methods:Patients were loaded with serine and with the amino acids glycine and alanine as controls and subsequently evaluated for the development of psychopathological symptoms. In addition, plasma levels of amino acids were measured.Results:In a subgroup of patients suffering from atypical psychoses, this biochemical challenge resulted in the reappearance of psychedelic symptoms in particular. Furthermore, significantly lower plasma concentrations of serine were found. In vitro experiments revealed a disturbance in the one-carbon metabolism. In another group of patients the loading provoked vegetative symptoms and fatigue.Conclusions:Disturbances in amino acid metabolism may be involved in the emergence of certain psychotic disorders.

scholarly journals Callus induction and plant regeneration of two Cuban rice cultivars using different seed explants and amino acid supplements

2009 ◽  
pp. 1-15
Author(s):  
Maylin Pérez-Bernal ◽  
Magalis Delgado Rigo ◽  
Carlos Alberto Hernández Díaz ◽  
María Teresa Barceló Ávila ◽  
Raúl Armas Ramos
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Culture Medium ◽  
Callus Formation ◽  
Callus Cultures ◽  
Rice Cultivars ◽  
Embryogenic Calli ◽  
Rice Callus

Most of Cuban rice cultivars are classified into indica subspecies, and they are inclined to poor in vitro response. In this paper we studied the role of endosperm and amino acids on callus formation of two Cuban rice cultivars: J-104 and IACuba-28. Callus cultures were initiated from three treatments for mature seed: intact seed, embryo with scutellum but without endosperm, and endosperm alone. It demonstrated the direct incidence of endosperm on in vitro seed contamination. But the higher percentage of embryogenic calli was obtained from intact seeds, despite of 12.94 % of seed contamination. Callus formation from endosperm alone did not occur. The role of endosperm to successful callus formation from scutellum was discussed. Effect of amino acids on rice callus growth from intact seeds was examined by supplying callus formation medium with glutamine and proline, separately or in combination, in both cultivars. Callus formation of J-104 was improved considerably with 500 mg/l of proline and glutamine in the culture medium, but in IACuba-28 were not observed significant changes. The percentage of embryogenic callus and the increase of fresh weight of calli were correlated with genotype and amino acid supplement in culture medium.

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