Hypocatalasia

Hypocatalasia, or acatalasemia, is an inherited metabolic disease affecting various kinds of animals incl. humans and dogs. As to dogs, the disease has been described in Beagles and American Foxhounds. It relates to reduced activity of the catalase enzyme that is commonly found in the red blood cells, in mucous membranes, in liver, muscles and skin. Its task is to protect the tissues from reactive oxygen species. The catalase deficiency leads to formation of ulcers and necrosis of soft tissues (also known as the gangrene). In dogs, this disease causes deep ulcers inside the mouth and periodontitis, particularly young dogs suffer from this disease.

This defect is caused by a point mutation G to A in position 979 (c.979G>A; p.Ala327Thr) in the CAT gene that leads to amino acid substitution with alanine replaced by threonine. This results in structural instability and deficiency of the enzyme and increased sensitivity to proteolytic degradation.

Mutation that causes Hypocatalasia is inherited as an autosomal recessive trait. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

The genetic testing can detect the heritable disease-related genotype of the individual and avoid producing dogs affected by hypocatalasia.

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Reference:

Nakamura, K., Watanabe, M., Takanaka, K., Sasaki, Y., Ikeda, T. : cDNA cloning of mutant catalase in acatalasemic beagle dog: single nucleotide substitution leading to thermal-instability and enhanced proteolysis of mutant enzyme International Journal of Biochemistry & Cell Biology 32:1183-1193, 2000.