764 XTI. VITAMINS K 



support these conclusions. However, redox potential is iiot the only 

 important consideration, since some of the naphthoquinones which had 

 no biopotency possessed appreciable redox potential values. 



It is not known what enzyme or enzymes may be concerned in the syn- 

 thesis of prothrombin. Naphthoquinones which possess biopotency have 

 been found to inhibit heart muscle succinoxidase,^^^ choline acetylase,^^"*-^'^ 

 and lactic acid-prockicing bacterial enzymes. "•'■''" Schonberg et aL"* 

 stated that the configuration of menadione and that of phytyl menadione 

 are theoretically and actually adequate for the Strecker degradation of 

 a-amino acids. Another suggestion is that the naphthoquinones may act 

 as plant respiratory pigments, for example juglon in the walnut, and 

 lawson in henna leaves. ^'^ This fits in with the finding that, in certain 

 plant leaves, vitamin K could be synthesized only if exposed to sunlight. ^-^^ 

 Erkama and Pettersson"^ observed that vitamin K formed in pea seedlings 

 in the absence of light, but to a much lesser degree than when they were 

 exposed to light. 



c. Vitamin K in Various T5T)es of Bleeding. A tendency to bleeding is 

 a rather common condition in some types of nutritional deficiency such as 

 scurvy, in hereditary hemophilia, and in thrombocytopenia. However, 

 vitamin K is of no value in any of these hemorrhagic conditions, except in 

 vitamin K deficiency. Table 1 summarizes the main characteristics of 

 several types of bleeding. 



According to Sebrell and Harris, '^^ serious abnormalities in blood coagula- 

 tion may be present in the absence of hemorrhage. They suggest that, 

 when the plasma prothrombin falls to 20% of the normal value, danger of 

 bleeding exists. When the prothrombin level exceeds this figure, bleeding 

 seldom occurs. However, Brinkhous and co-workers^^ have suggested 

 that the danger level for prothrombin is 35 to 20%, and Roller and Frick'-' 

 recorded a figure as low as 5% of normal as the critical prothrombin \e\e\. 



The bleeding in vitamin K deficiency may first be recognized by slow 

 oozing from the mucous membranes of the nasopharynx, by the occurrence 



"3 E. G. Ball, C. B. Anfinsen, and O. Cooper, /. Biol. Chem., 168, 257-270 (1947). 



"" C. Torda and H. G. Wolff, Proc. Soc. Exptl. Biol. Med., 57, 2.36-239 (1944). 



"s C. Torda and H. G. Wolff, Science, 103, 645-646 (1946). 



"8 W. D. Armstrong, W. W. Spink, and J. Kahnke, Proc. Soc. Exptl. Biol. Med, 53, 

 230-234(1943). 



1" P. Atkins and J. L. Ward, Brit. J. Exptl. Pathol., 26, 120-124 (1945) 



"8 A. Schonberg, R. Moubasher, and A. Said, Nature, 164, 140 (1949). 



"9 J. Erkama and N. Pettersson, Acta CHem. Scand., 4, 922-925 (1950). 



120 W. H. Sebrell, Jr. and R. S. Harris, The Vitamins, Vol. II, Acad. Press, New York, 

 1954, pp. 387-448, p. 420. 



1" F. Roller and P. Frick, Helv. Chim. Acta, 32, 717-722 (1949). 



