PEDBASE.org - The Pediatric Database - Detailed information of ACATALASEMIA

ACATALASEMIA

DEFINITION:

A disorder of peroxisomes characterized by a deficiency in catalase activity resulting in 2 clinical variants.

incidence: 1/250,000
age of onset:
- prior to puberty
risk factors:
- familial - autosomal recessive
  - chrom. #: 11p13
  - gene: catalase

structure:
- gene 34 kb in length with 12 introns and 13 exons
- gene codes for a protein of 526 aa but the erythrocycte catalase is 517 aa suggesting some sort of post-translational processing takes place
- a tetramer containing a ferric (heme) iron which reacts readily with hydrogen peroxide
function:
- the main function is the conversion of hydrogen peroxide to water and oxygen
- catalase is part of a cluster of antioxidant enzymes (superoxide dismutase, peroxidases) which act in concert to protect cells against activated oxygen species (oxygen with an extra oxygen usually produced by neutrophils)
- protects hemoglobin against oxidation by hydrogen peroxoide and perhaps peroxide-mediated damage to DNA

considered to be a disorder of lipid metabolism and particularly the peroxisomes
a genetically heterogeneous disease with two major variants:

mutation in the regulatory portion of the gene
deficiency of catalase activity arises from the synthesis of an enzyme with low specific activity or from diminished synthesis

mutation in the structural portion of the gene
deficiency of catalase activity arises from the production of an unstable form of catalase

catalase activity deficiency predisposes patients to infection by peroxide-generating bacteria such as streptococci and pneumococci as erythrocycte catalase may not be able to protect heterologous tissue from damage by exogenous hydrogen peroxide
another hypothesis is that hydrogen peroxide accumulation in areas of infection may induce neutrophil dysfunction
heterozygotes present as hypocatalasemia and are unaffected

oral ulcerations and gangrene
(streptococcal and pneumococcal infections may start as small lesions around the gingival-dental border or on the tonsils and develop into fulminating inflammatory processes causing extensive tissue destruction, i.e., gums)
a relatively benign disease with no other clinical features

reduced catalase activity in RBC's
blood placed in contact with hydrogen peroxide turns brown and does not produce oxygen bubbles

no treatment for underlying disorder
multidisciplinary approach:
- aggressive treatment of streptococcal and pneumococcal infections
- close dental monitering and surgery if necessary

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