586 XII. HEMOGLOBIN CATABOLISM, II 



3.3. Excretion of Porphyrins 



3.3.1. Introduction. Porphyrin was first observed in the human 

 urine by Baumstark in 1874 {195). In 1891 Salkowsky found it in 

 the urine after sulfonal administration {;2J^18). Soon afterward 

 Garrod published his classic studies on what we now call porphyrias, 

 congenital diseases in which large amounts of porphyrin are excreted 

 in the urine. Among the pioneers were Saillet {2Jf.lJf.) and Stockvis 

 {2671). Saillet and Garrod were the first to discover small amounts 

 of porphyrin in the normal human urine. 



At that time hematoporphyrin was the only porphyrin known, and 

 the term "hematoporphyrinuria" is still used in many medicine and 

 physiology textbooks {cf. 261 Jf). We now know from the work of 

 H. Fischer and Schumm that the porphyrin predominant in both 

 feces and normal urine is coproporphyrin. This is accompanied in 

 the urine by traces of uroporphyrin (^49-4)- Protoporphyrin does not 

 occur in the urine. One claim that it does so, by Boas {299), is evi- 

 dently due to a confusion with mesobiliviolin. 



3.3.2. Excretion of Porphyrins of Isomeride Types I and III. 



We have discussed the isomerism of porphyrins in Chapter III and 

 have seen that of the four possible types of isomerides of porphyrins 

 which contain four each of two different kinds of side chains, such 

 as copro- and uroporphyrins, only two are found in nature, type I 

 with alternating arrangement and type III with dissymetrical arrange- 

 ment. The protoporphyrin of hemoglobin and that found free in 

 nature have always been of type IX {cf. above), which on conversion 

 to coproporphyrin would yield coproporphyrin III. From the struc- 

 ture of the porphyrins of type I and type III it is clear that a con- 

 version of one to the other cannot occur without far-reaching decom- 

 position and resynthesis, which is unlikely (dualism of the porphyrins, 

 H. Fischer). 



It is of historical interest and necessary for the understanding of Fischer's 

 earlier papers to note that his term "dualism of the porphyrins" had at first 

 a different meaning. It referred to the difference between proto- and copro- 

 porphyrins, and it was then assumed that a similar dualism of hemoglobins 

 existed, protoporphyrin being derived from hemoglobin, coproporphyrin from 

 myohemoglobin {e.g., Fischer and Schneller, 876). This idea had later to 

 be abandoned, but the same term was then used in the new meaning. 



In 1939 Fischer {795) claimed to have obtained evidence for a 

 type II mesoporphyrin occurring in hemoglobin. This evidence, 



