Transglutaminase-dependent formation of protein aggregates as possible biochemical mechanism for polyglutamine diseases

Transglutaminases (Enzyme Commission 2.3.2.13) are a large family of enzyme s that show the common capacity to catalyze cross-linking of protein substr ates. Some members of this family of enzymes are also capable of catalyzing other reactions important for the cell life. The distribution and the role of these enzymes have been widely studied in numerous cell types and tissu es, but only recently their expression and functions started to be investig ated in the central nervous system. One of the main biochemical properties of the transglutaminase enzymes is to form large protein aggregates that ar e insoluble in all known protein detergents, such as urea, guanidinium, and sodium dodecyl sulfate. Recently, the transglutaminase activity has been h ypothesized to be involved in the pathogenetic mechanisms responsible for t he formation of cellular inclusions present in Huntington disease and in al l the other polyglutamine (polyQ) diseases hitherto identified, such as spi nobulbar muscular atrophy or Kennedy disease, spinocerebellar ataxias (SCA- 1, SCA-2, SCA-3 or Machado-Joseph disease, SCA-6 and SCA-7) and dentatorubr opallidoluysian atrophy. In this review we describe the biochemical propert ies of the transglutaminase enzymes and some recent findings about the phys iopathological roles played by these enzymes in the central nervous system. (C) 2001 Elsevier Science Inc.