Study Of Changes In Protein Expression In The Key Amino Acids Metabolic Pathways In Streptococcus Thermophilus MN-ZLW-002 During Culture

Streptococcus thermophilus is one of the most widely used as a starter strain in the dairy industry.The amino acids metabolism of S.thermophilus has a profound effect on the quality of fermented food in industrial production.Therefore,the expression levels of proteins involved in the amino acids metabolism pathways were deeply studied in this experiment,in order to increase the knowledge of the changes of the proteins related to amino acids metabolism in S.thermophilus,providing the theoretical support for the regulation mechanism of S.thermophilus during high-cell-density culture.In this experiment,S.thermophilus MN-ZLW-002 was used as the experimental strain,and S.thermophilus MN-ZLW-002 was fermented under p H controlled bactch fermentation through the addition of sodium hydroxide in chemical defined medium.The proteomics technoloy was used to analyze the key proteins in the amino acids metabolic pathways at the four key growth points of S.thermophilus MN-ZLW-002 to elucidate the changes of key proteins in the major amino acids metabolic pathways.Based on proteomic data analysis,a total of 1,560 proteins were identified,of which 134 were involved in amino acids transport and metabolism,accounting for 8.59% of the total proteins.Among the proteins related to amino acids metabolism,the proteins involved in the metabolism of cysteine and methionine were the most,accounting for 17.16% of the total amino acid metabolism proteins.D-alanine mainly generated poly-O-D-alanyl(ribitol phosphate)and D-alanyl-D-alanine,glutathione mainly produced L-cysteine and glutathione disulfide,aspartic acid mainly converted tofumarate,oxaloacetate and N-carbamoyl-L-aspartic acid,glutamate mainly converted tophosphoribosamine and carbamyl,serine mainly produced pyruvic acid,cysteine mainly produced pyruvic acid,3-mercaptoacetate and S-adenosyl-L-methionine.Lysine synthesis mainly occurred in late-lag phase,the syntheses of phenylalanine and tyrosine mainly occurred in late-exponential and stationary phases,arginine synthesis mainly occurred in late-exponential and stationay phases.The key proteins involved in the D-alanine metabolic pathway were the transaminase Ala A,D-alanyl-D-alanyl ligase Ddl and D-alanine-poly(phosphatidyl)ligase Dlt A.The key proteins involved in the glutathione metabolic pathway were glutathione synthetase Gsh A,phosphoglucose dehydrogenase Gnt Z,glutathione peroxidase Gpx,glutathione in dipeptidase Pep D and glutathioneReductase GSR.The key proteins involved in the aspartate and threonine metabolic pathways were aspartate carbamoyltransferase PyrB,L-asparaginase Asn A,adenyl succinate synthetase PurA,adenyl succinate lyase PurB,arginine succinate synthetase ArgG,argininosuccinate lyase Arg H,aspartate racemase RacD,aspartate aminotransferase AspB,aspartate-semialdehyde dehydrogenase Asd and day Aspartate kinase Lys C.The key proteins involved in the glutamate metabolic pathway were glutamate decarboxylase Gad B,succinate semialdehyde dehydrogenase Gab D1,Gab D2,glutamate dehydrogenase Gdh A,glutamine-fructose-6-phosphate aminotransferase GlmS,Amido phosphoribosyltransferase Gur F and carbamoyl phosphate synthase Car B,Car A.The key proteins involved in the metabolism of glycine and serine were2-hydroxyacid dehydrogenase Ghr A,histidine phosphatase protein Gpm B,2-oxoglutarate reductase Ser A,methyltransferase Gsmt and methyltransferase Sdmt.The key proteins involved in the lysine synthesis pathwaywere aspartate kinase Lys C,aspartate-semialdehyde dehydrogenase Asd,4-hydroxy-tetrahydrodipyridylate reductase Dap B,and tetrahydrodipyridylate reductase Dap H,transaminase PatA,succinate diaminotransferase DapE,diaminopimelate epimerase DapF and diaminoheptanoate decarboxylase LysA.The key proteins involved in the synthesis pathways of phenylalanine and tyrosine were 3-deoxy-7-phosphate heptanesulfonic acid synthase AroA2,3-dehydroshikimate synthase AroB,dehydrohumulic acidase AroD,and shikimic acid Hydrogenase Aro E,3-carboxyvinyltransferase 1-carboxyvinyltransferase AroA,chorismate synthase AroC,aspartate transaminase Asp B,histidine phosphate aminotransferase His C and prephenate dehydrogenase TyrA2.The key proteins involved in the metabolic pathways of cysteine and methionine were cystathionine ?-synthase MetC,cystine synthase CysK,aspartate aminotransferase AspB,L-lactate dehydrogenase Ldh and Homocysteine protein Met E.The key proteins involved in the arginine metabolic pathway were carbamate kinase ArcC,aspartate aminotransferase Asp B,transaminase Ala A,glutamate dehydrogenase Gdh A,ornithine carbamoyltransferase Arg F,arginine amber Acid synthase Arg G,arginine deiminase ArcA and argininosuccinate lyase ArgH.