|
Distribution and pathophysiologic role of molybdenum-containing enzymes
Y. Moriwaki, T. Yamamoto and K. Higashino
Third Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan
Offprint requests to: Dr. Yuji Moriwaki, M.D. , Third Department of
Internal Medicine, Hyogo College of Medicine, Mukogawa-cho 1-1 ,
Nishinomiya, Hyogo 663, Japan
Summary. The importance of molybdenum-containing
enzymes in the pathophysiology of a number of clinical
disorders necessitates a comprehensive understanding of
their histological localization and expression. The
objectives of this review are to cover such enzymes so
far reported and their enzyme- and immunohistochemical
localization in various tissues and species, and
to discuss their possible pathophysiological effects.
The molybdenum cofactor is essential for the
activity of the three molybdenum-containing enzymes,
sulfite oxidase, xanthine oxidase and aldehyde oxidase.
Sulfite oxidase serves as the terminal enzyme in the
pathway of the oxidative degradation of sulfur amino
acids, and is also involved in preventing the toxic effects
of sulfur dioxide. Biochemical study has revealed a high
activity of sulfite oxidase mainly in the liver, heart and
kidney with lesser activity observed in other tissues.
Subcellular observations have shown that this enzyme is
present in the mitochondrial intermembraneous spaces.
Xanthine oxidase is the final enzyme in the conversion
of hypoxanthine to xanthine, and subsequently, to uric
acid. Unlike sulfite and aldehyde oxidases, xanthine
oxidase can be converted to xanthine dehydrogenase,
and vice versa. Xanthine oxidase has been widely
inves tigated for its role in post- ischemic reperfusion
tissue injury. Enzyme- and immunohistochemical studies
of its localization in various animal species and ti ssues
have shown its ubiquitous di stribution in the liver, small
and large intestine, lung and kidney, and other tissues.
Aldehyde oxidase shares a similar substrate specificity
with xanthine oxidase. Although the ti ssue localization
of this enzyme has not been studied as thoroughly as that
of xanthine oxidase, aldehyde oxidase is reportedly
found in the digestive gland of terrestrial gastropods, the
antennae of certain moths as well as the mammalian
liver. Recently, the ubiquitous distribution of aldehyde
oxidase has been demonstrated in rat tissues. The
aldehyde oxidase activity of herbivores exceeds that of
carnivores, suggesting a possible role of this enzyme as a
protection against the effects of toxic plants. The
relationship between the ti ssue localization of these
enzymes and their pathophysiological roles is reviewed. Histol Histopathol 12, 513-524
(1997)
Key words: Molybdenum-containing enzyme, Sulfite
oxidase, Xanthine oxidase, Aldehyde oxidase, Tissue
distribution, Histochemistry, Pathophysiology
DOI: 10.14670/HH-12.513
|