Publisher Summary The thrombin-induced conversion of fibrinogen to fibrin that is the primary subject of this review is essentially the final stage in the complex series of processes involved in blood coagulation. Fibrinogen exists in normal blood, while thrombin is present as its precursor prothrombin. The coagulation process consists of the conversion of prothrombin to thrombin and of the subsequent action of thrombin on fibrinogen to produce fibrin. In the fibrinogen-fibrin conversion fibrinogen, already a high polymer of many amino acids is converted to an even higher polymeric form or coagulum, the fibrin clot. Prothrombin can be converted to thrombin in a series of highly complex, and as yet not well understood, reactions. The chapter explores four of the processes by which the conversion of prothrombin to thrombin takes place. These are (1) activation by citrate, (2) activation by calcium ions, Ac-globulin and thromboplastin, (3) activation by calcium ions, platelets and thromboplastin, and (4) activation by trypsin. The chapter concludes by addressing the various problems of current interest in protein chemistry, which appear in the study of the fibrinogen-fibrin conversion. The first step is an example of a limited proteolysis by a protease of curious specificity. This proteolysis may turn out to be one of the first illustrations of the existence of “strong” peptide bonds in proteins. Further, it offers a nice illustration of the phenomenon of unmasking or activation in biological systems. The second step involves protein-protein associations with unequal association constants. The last step may involve gel formation or crystallization.

The Fibrinogen-Fibrin Conversion1

an thocyanb i ldung a n w e n d b a r ist, wi rd zum Gegens tand wei terer U n te r suc hnngen gemacht . Auch zu der neuerdings yon SEYBOLD a) aufgeworfenen Frage, wie wef t die physiologischen Analogien zwischen Pe ta len und herbs t l i ehen Laubb l~ t te rn gehen, k6nnen zur Zei t laufende Un te r suehungen m a n e h e n Hinweis geben. In fas t allen F~tllen konn te im Herbs t l aub nach der yon PAEC~ und ROCKEZqB~OD *) angegebenen N e t h o d e Iiaffees~iure nnd Chlorogens~iure in aufIallend hoher Konzen t r a t i on naehgewiesen werden. Nach neueren Arbe i ten stell t die IKaffees~iure eine Vors tufe bet der Biosyn these des Quercet ins darT). Nine ausfi ihrl iche Mit te i lung der Ergebnisse wird an anderer Stelle erfolgen.

Amino-acid constituents of fungal alpha-amylase

SEEGERS et al.
1 have very recently made an analysis on the amino-acid content, particularly tyrosine and tryptophan, of purified prothrombin. They have also shown by electrophoresis that their prothrombin preparation contains approximately 90 per cent of the protein in one component1. Several other workers2–4 have investigated the nature of the protein in prothrombin. Astrup and Darling4 have reported prothrombin to be a protein of globulin character. But the complete analysis of the prothrombin molecule with respect to different amino-acid contents is lacking.

Gauranga Ray

Papers

Identification of amino-acids present in purified prothrombin by circular paper chromatography.

Effect of some metal ions on the activation of prothrombin