title: Plant phytaspases and animal caspases: structurally unrelated death proteases with a common role and specificity.
abstract: Proteases with an aspartate cleavage specificity are known to contribute to programmed cell death (PCD) in animals and plants. In animal cells this proteolytic activity belongs to caspases, a well-characterized family of cysteine-dependent death proteases. Plants, however, lack caspase homologs and thus the origin of this type of proteolytic activity in planta was poorly understood. Here, we review recent data demonstrating that a plant serine-dependent protease, phytaspase, shares cleavage specificity and a role in PCD analogous to that of caspases. However, unlike caspases, regulation of phytaspase-mediated cleavage of intracellular target proteins appears to be attained not at the level of proenzyme processing/activation, which occurs, in the case of phytaspase, autocatalytically and constitutively. Rather, the mature phytaspase is excluded from healthy cells into the apoplast and is allowed to re-enter cells upon the induction of PCD. Thus, PCD-related proteases in animals and plants display both common features and important distinctions.
authors.affiliation: Department of Chemistry and Biochemistry of Nucleoproteins, AN Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
authors.forename: Nina V
authors.initials: NV
authors.lastname: Chichkova
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Tuzhikov
authors.forename: Michael
authors.initials: M
authors.lastname: Taliansky
authors.forename: Andrey B
authors.initials: AB
authors.lastname: Vartapetian
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism*; D020134:Catalytic Domain; D016923:Cell Death; D004789:Enzyme Activation; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000821:virology; D010940:Plant Proteins / Q000378:metabolism*; D059748:Proteolysis; D013045:Species Specificity; D013379:Substrate Specificity; D013381:Subtilisins / Q000378:metabolism; D014026:Nicotiana / Q000201:enzymology* / Q000821:virology; D014027:Tobacco Mosaic Virus / Q000187:drug effects / Q000472:pathogenicity
chemical_list: D000998:Antiviral Agents; D010940:Plant Proteins; D013381:Subtilisins; C119297:subtilase, plant; D020169:Caspases