Reduced hæmatin and hæmochromogen

Abstract

Hæmochromogen, which originally was known only as an artificial degradation product of hæmoglobin, has since been found to occur in almost all organisms. Helicorubin, a hæmochromogen occurring in the intestinal fluid of snails (such as Helix pomatia) was described by Krukenberg (1884), and its properties examined by Dhéré (1917). Cytochrome has been shown by Keilin (1925) to be a mixture of at least two, possibly three, hæmochromogens. Just as hæmoglobin differs in its behaviour towards oxygen from any of the other compounds of hæmatin at present known, so most of the naturally occurring hæmochromogens differ in properties from any of the artificial hæmochromogens. Ordinary hæmochromogen, obtained directly from hæmoglobin, combines with carbon monoxide to give CO-hæmochromogen, and is rapidly oxidised under all conditions by free oxygen to hæmatin. The hæmochromogens of cytochrome do not combine with carbon monoxide, and with the exception of component b (Keilin, 1929) are not rapidly oxidised by free oxygen over definite ranges of hydrogen-ion concentration. Originally hæmochromogen was only a name for the spectrum of reduced hæmatin under special conditions. Zeynek (1920) had shown by an analysis of solid pyridine hæmochromogen that it contains 2·2 molecules of pyridine. Anson and Mirsky (1925) were the first to show that this particular type of hæmatin spectrum is due to chemical combination of reduced hæmatin with substances containing nitrogen, and that each nitrogen compound gave its characteristic hæmochromogen. They showed that these compounds were dissociable in solution, and also that the various nitrogen compounds were in equilibrium with the hæmochromogen according to their relative affinities. Late I (1926) measured the minimum quantity of pyridine required to change completely the spectrum of reduced hæmatin into hæmochromogen, using strong solutions of hæmatin, and found that 2 molecules per molecule of reduced hæmatin were required, which agreed with Zeynek's analysis.