CHAPTER X 



CHEMICAL MECHANISM OF BILE PIGMENT 



FORMATION AND OTHER IRREVERSIBLE 



ALTERATIONS OF HEMOGLOBIN 



1. INTRODUCTION AND NOMENCLATURE 



In this chapter we discuss the chemical mechanism of bile pigment 

 formation from hemoglobin and other hematin compounds and a 

 number of irreversible alterations of hemoglobin, which may be 

 closely related to the formation of intermediates between hemoglobin 

 and bile pigments. 



That bile pigments arise in the animal body by a breakdown of 

 hemoglobin, has been generally accepted for a long time (c/. Chapter 

 XI). The mechanism of this transformation, however, remained 

 mysterious. The direction of the search was wrong, first, in assuming 

 that hematin and porphyrin could be considered as likely inter- 

 mediates, and, second, in attempting to find a conversion to bilirubin, 

 which was assumed to be the primary bile pigment. 



In 1935 Lemberg {1681) described the transformation of hematin 

 into biliverdin. As intermediates in this process he found green 

 complex iron compounds, previously described by Warburg and 

 Negelein {2952) as "green hemin," which he called "verdohemo- 

 chromogens," and which we shall now call verdohemochromes, in 

 conformity with the nomenclature suggested in Chapter V. They 

 are hemochromes {e.g., pyridine hemochromes) which contain a 

 tetrapyrrolic compound closely related to and easily convertible into 



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