Assuntos
Catepsinas/metabolismo , Endopeptidases/metabolismo , Frutose-Bifosfato Aldolase/metabolismo , Fígado/enzimologia , Metaloendopeptidases , Músculos/enzimologia , Subtilisinas/farmacologia , Sequência de Aminoácidos , Aminoácidos/metabolismo , Animais , Carboxipeptidases/metabolismo , Carboxipeptidases A , Catepsina B , Substâncias Macromoleculares , CoelhosRESUMO
Two new peptides, designated thymosin beta 8 and thymosin beta 9, respectively, have been isolated and their amino acid sequences established. Thymosin beta 8, isolated from calf thymus fraction 5, has a mass of 4518 daltons and contains 39 amino acid residues, of which 31 are identical to the corresponding amino acid residues in thymosin beta 4 isolated from the same source. The NH2 terminus of thymosin beta 8 is acetylalanine, compared with acetylserine in thymosin beta 4. Thymosin beta 9, isolated from fresh-frozen calf thymus by a procedure that minimizes proteolysis, is identical to thymosin beta 8 except for the presence of an additional dipeptide, -Ala-LysOH, at the COOH terminus. It has a mass of 4717 daltons and 32 of its 41 amino acids are identical to those of thymosin beta 4. The similarity in structures of thymosin beta 4 and thymosin beta 9 suggests that they may have related functions.
Assuntos
Timosina/isolamento & purificação , Timo/análise , Hormônios do Timo/isolamento & purificação , Animais , Bovinos , Cromatografia Líquida de Alta Pressão , Timosina/análiseRESUMO
The ability of rabbit liver aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphatate-lyase, EC 4.1.2.13) and rabbit liver fructose-1,6-bisphosphatase (Fru-P2ase; D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) to partition into the gel phase of Ultrogel AcA 34 is decreased in a mixture of the two enzymes. Titration experiments indicate that a 1:1 complex is formed. The value for the distribution coefficient of the complex corresponds to a molecular mass of 300,000 daltons, the value expected for a dimer containing one mole of each enzyme protein. Complex formation was not observed when either liver enzyme was replaced by the corresponding isozyme from rabbit muscle. The susceptibility of liver Fru-P2ase to limited proteolysis by subtilisin was reduced in the presence of liver aldolase, but not when the latter was replaced by muscle aldolase, suggesting that the conformation of Fru-P2ase is altered in the complex. Limited proteolysis of liver aldolase abolishes its ability both to form the heterodimer and to protect Fru-P2ase from modification by subtilisin.
