MacMunn, Charles

Charles MacMunn (1852-1911)

Discovery of Respiratory Pigments – The Cytochrome System

Charles MacMunn was born in Seafield House, Easkey, Sligo. He showed great interest in nature as a child. His father, also a doctor, sent him to Trinity College Dublin to study medicine, where he qualified in 1872. While he was a student in the Meath hospital in Dublin, he was encouraged by William Stokes to study spectroscopy.

The spectroscope was used in astronomy for clues to the chemistry of stars from analysis of absorption patterns in the spectrum of light. William Stokes’ cousin in Cambridge had worked out the function of haemoglobin (Hb) by studying the spectral changes in arterial and venous blood.

After MacMunn qualified, he joined his cousin’s practice in Wolverhampton, England. There he started to study body tissues with a microspectroscope. He also had an eyepiece drilled through the wall of his study to scrutinise patients approaching, so that he could claim he was too busy for those he did not want to examine!

McMunn discovered respiratory pigments throughout plant and animal tissues. He named them histohaematin and myohaematin, and showed that the chemistry of energy production in the body took place deep in the cellular structure of the tissues, and not just in the blood as had been previously surmised.These respiratory pigments are now known as cytochromes, and are fundamental to energy metabolism.

Despite his researches and published papers, there was little recognition of his discovery in his lifetime. In fact he was attacked by the prestigious German biochemist Hoppe-Seyler, who claimed that MacMunn’s pigments were breakdown products of haemoglobin, despite the fact that MacMunn had taken great care to exclude this possibility.This attack greatly discouraged MacMunn who ceased his researches, but continued his medical practice. He had a distinguished career in the army, and in civil life. However the malaria, that he contracted in South Africa during the Boer war, plagued him for the rest of his life. He died in 1911. His book on his research was published posthumously by his wife, and was dedicated lovingly to her.

Cytochromes were rediscovered in 1925, by David Keilin, a Polish parasitologist in Cambridge, who recognised MacMunn’s achievement and vindicated his original discovery. MacMunn had shown key chemical intricacies of tissue respiration to medical science.

References:

1.        Coakley, D.   (1997) Irish Masters of Medicine. Town House.

2.        Snyder, R. (2000) Cytochrome P450, the Oxygen-Activating Enzyme in Xenobiotic Metabolism. Toxicological Sciences 58, 3-4.

3.        Slater, EC   Keilin. (2003) Cytochrome, and the Respiratory Chain. J Biol Chem., Vol. 278, Issue 19, 16455-16461.