Canine Catalase Deficiency (CAT)
Canine catalase deficiency (CAT), also known as acatalasemia or hypocatalasia, is a genetic disorder characterized by impaired catalase activity in the erythrocytes. Canine CAT has been identified in the Beagle and American Foxhound breed. The affected dogs have a higher risk of developing open sores (ulcers) inside the mouth that may lead to the death of soft tissue, also known as the gangrene. Except in dogs, acatalasemia has been diagnosed also in humans and mice. In humans, affected patients have an increased risk of developing type 2 diabetes mellitus.
Characteristics and Symptoms
During respiration of all aerobic organisms, reactive oxygen species are generated. One such reactive oxygen species is hydrogen peroxide, which has a high potential to react with different compounds within the cell due to its instability. Although hydrogen peroxide has various important roles within the organisms, such as in the immune system defense, in concentrations higher than regular it causes soft and hard tissue damage, is capable of damaging DNA, protein and lipid membranes and can be linked to cancer. Catalase is an enzyme found in nearly all living organisms, where it converts hydrogen peroxide to water and oxygen, and by that plays a vital role in the antioxidative defense.
Affected dogs are most commonly asymptomatic and the disorder is usually diagnosed when checking other symptoms or through the family tree. When the symptoms are present, they usually include oral gangrene and ulcers.
Canine catalase deficiency (CAT) is caused by a missense mutation in the CAT gene, which causes a thermal instability of the mutant catalase enzyme in the erythrocytes. The instability causes 8-fold faster degradation of the enzyme than in a healthy dog. Measurement of enzyme activity shows no signs of catalase activity in the erythrocytes of the affected dog.
The disorder is suspected to be inherited in an autosomal recessive pattern, but that yet must be determined.
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. Int J Biochem Cell Biol 32:1183-1193, 2000.
Nakamura K, Watanabe M, Sasaki Y, Ikeda T. Purification and characterization of liver catalase in acatalasemic beagle dog: comparison with normal dog liver catalase. Int J Biochem Cell Biol 32:89-98, 2000. Ogata M, Wang DH, Ogino K. Mammalian acatalasemia: the perspectives of bioinformatics and genetic toxicology. Acta Med Okayama 62(6):345- 361, 2008.