Search PubMed⌕ Search

Biomedical subjects

K Titani

Publications and source records attributed to K Titani.

At least 271 records · Page 15Linked to original sources
PubMed1975

Bovine factor X1 (Stuart factor). Primary structure of the light chain.

The amino-acid sequence of the light chain of bovine factor X1 is presented. The sequence of 112 of the 140 residues was determined automatically on fragments produced by specific cleavage of arginyl, glutamyl, tryptophanyl, and asparaginyl-glycine bonds. The remainder was determined by conventional procedures. The amino-terminal sequence of the light chain is homologous with the amino-terminal region of bovine prothrombin and, like the latter, appears to contain several residues of a recently discovered unusual amino acid, lambda-carboxy-glutamic acid. The role of this amino acid in the calcium-binding ability of factor X and prothrombin is discussed.

Amino Acid Sequence↗
PubMed1975

Amino-acid sequence of bovine carboxypeptidase B.

The amino-acid sequence of bovine carboxypeptidase B [peptidyl-L-lysine(-L-arginine)hydrolase, EC 3.4.12.3] has been determined using the heavy and light chains of the enzyme isolated from spontaneously activated pancreatic juice. Comparison of the sequence with that of carboxypeptidase A shows that the two enzymes are homologous (49% identity) and that all but one of the functional residues identified in carboxypeptidase A occur in corresponding loci in carboxypeptidase B (peptidyl-L-amino acid hydrolase, EC 3.4.12.2). The exception is the replacement of Ile-255 at the bottom of the substrate binding pocket of carboxypeptidase A, by aspartic acid in carboxypeptidase B. This single change can account for the difference in specificity of the two enzymes.

Amino Acid Sequence↗
PubMed1975

Bovine factor X1 (Stuart factor): amino-acid sequence of heavey chain.

The amino-acid sequence of the heavy chain of bovine blood coagulation factor X1 (Stuart factor) isolated before and after activation has been determined. Sequence analysis was performed on fragments obtained by cleavage with cyanogen bromide and by tryptic digestion. Comparison of the complete sequence with those of other hepatic and pancreatic serine proteases demonstrates homology of the heavy chain of activated factor X1 (factor X1a) with the B chain of bovine thrombin as well as with bovine trypsin, chymotrypsins A and B, and porcine elastase. The activation peptide cleaved near the amino terminus by a protease from Russell's viper venom differs in both size and sequence from those of other serine proteases. With three exceptions, all of the residues which are important in the catalytic functions of trypsin and chymotrypsin occur in corresponding loci in the heavy chain of factor Xa. These finding suggest that the three-dimensional structure of the heavy chain is similar to that of the pancreatic serine proteases and that these enzymes have evolved from a common ancestral gene.

Amino Acid Sequence↗
PubMed1975

Activation of bovine factor X (Stuart factor): conversion of factor Xaalpha to factor Xabeta.

Bovine factor X (molecular weight 55,100) is a blood coagulation factor present in plasma in a precursor or zymogen form. It is a glycoprotein which has been isolated as a two-chain structure held together by one or more disulfide bonds. During the coagulation process, factor X is converted to a serine protease by the hydrolysis of a specific peptide bond in the amino-terminal region of the heavy chain. This cleavage occurs between Arg-51 and Ile-52, giving rise to factor Xaalpha (molecular weight 45,300) and an activation peptide (molecular weight 9500). Factor Xaalpha is then converted to factor Xabeta (molecular weight 42,600) by hydrolysis of a second specific peptide bond in the carboxyl-terminal region of the heavy chain. This cleavage occurs between Arg-290 and Gly-291, giving rise to a second glycopeptide (molecular weight 2700). Factor Xaalpha and factor Xabeta have equivalent coagulant activity, indicating that the cleavage of the second peptide bond is unrelated to the activation process.

Amino Acid Sequence↗
PubMed1974

A comparison of bovine prothrombin, factor IX (Christmas factor), and factor X (Stuart factor).

A comparison has been made of the electrophoretic behavior, chemical composition, amino-terminal sequence, and immunological properties of bovine prothrombin, factor IX (Christmas factor), and factor X (Stuart factor). Some immunological crossreactivity was found between the antibody to prothrombin and factor X although prothrombin and factor X differ substantially in amino-acid and carbohydrate composition. Considerable amino-acid sequence homology was found in the amino-terminal portion of prothrombin, factor IX, and the light chain of factor X. These data provide further evidence to support the hypothesis that at least three of the vitamin K-dependent clotting factors have evolved from a common ancestral gene.

Amino Acid Sequence↗