64 The Chemistry of the Injured Cell 



jury by virtue of its peculiar properties, may possibly be seen in the 

 action of some bacterial toxins. Thus the a toxin of Clostridium 

 welchii is a lecithinase which attacks phospholipids, important con- 

 stituents of cell walls. This toxin in fact haemolyses red cells and 

 disrupts isolated mitochondria. 



DEFICIENCY STATES 



Folic acid and cyanocobalamin (vitamin Bi 2 ) and its constitu- 

 ent cobalt may be deficient in man and animals and this lack may 

 lead to anaemia and neurological disease. The two substances ap- 

 pear to be involved with the synthesis and interconversion of nu- 

 cleic acids. Vitamin Bi 2 is also involved in the transmethylation 

 of methionine. The connection between these actions and the 

 clinical results of their deficiency is unknown. Similarly, ascorbic 

 acid (vitamin C) apart from aiding the metabolism of tyrosine, may 

 be necessary to control the redox potential of cells. However, the 

 link between these enzymic effects and scurvy (clinical vitamin C 

 deficiency) remains tenuous. 



GENETICALLY DETERMINED ENZYME DEFICIENCIES 



(See also Harris, 1959) 



A. Red Corpuscles 



Sickle cell anaemia is a hereditary disease in which the red cells 

 assume a characteristic sickle cell form, especially when subjected 

 to low oxygen tensions. The condition appears to be due to an ab- 

 normality in the synthesis of the globin constituent of haemoglobin 

 which is then present in a form that differs from normal in its 

 electrophoretic pattern. This abnormal haemoglobin has the 

 property of crystallising at low oxygen tensions, a feature which 

 explains the distortion and framentation of red cells seen in sickle 

 cell anaemia. In severe cases, this effect is seen at the oxygen tension 

 of venous blood so that sickling is present continuously. 



Another example is congenital methaemoglobinaemia. Here 

 there is inability to reconvert methaemoglobin (normally formed 

 continuously in small amounts) to haemoglobin. The disease is 



