Journal:Acta Cryst D:S2059798324005461
From Proteopedia
(Difference between revisions)
| Line 12: | Line 12: | ||
==Division of ASNases into three classes== | ==Division of ASNases into three classes== | ||
So far, three completely different structural classes of ASNases have been identified<ref>PMID:34258001</ref>, originally named according to the source organism of their isolation<ref>PMID:17143335</ref>, namely Class 1 (bacterial-type), Class 2 (plant-type), and Class 3 (Rhizobium etli-type). This newer classification is intersected with an older convention, which divided the known enzymes with L-asparaginase activity into five types, since in both, Class 1 and Class 3, two types are distinguished according to their compartmentalization and expression profile. The prototypes of types I and II (in Class 1), and III (in Class 2), are the ''E. coli'' enzymes EcAI (cytosolic), EcAII (periplasmic), and EcAIII (also cytosolic), respectively. The prototypes of types IV and V (Class 3) are the R. etli enzymes ReAIV (constitutive) and ReAV (inducible). | So far, three completely different structural classes of ASNases have been identified<ref>PMID:34258001</ref>, originally named according to the source organism of their isolation<ref>PMID:17143335</ref>, namely Class 1 (bacterial-type), Class 2 (plant-type), and Class 3 (Rhizobium etli-type). This newer classification is intersected with an older convention, which divided the known enzymes with L-asparaginase activity into five types, since in both, Class 1 and Class 3, two types are distinguished according to their compartmentalization and expression profile. The prototypes of types I and II (in Class 1), and III (in Class 2), are the ''E. coli'' enzymes EcAI (cytosolic), EcAII (periplasmic), and EcAIII (also cytosolic), respectively. The prototypes of types IV and V (Class 3) are the R. etli enzymes ReAIV (constitutive) and ReAV (inducible). | ||
| + | |||
| + | ==Structural studies== | ||
| + | The first L-asparaginase structure was published and deposited in the PDB in 1993 for the EcAII enzyme<ref>PMID:8434007</ref> and may serve as an example of a Class 1 type II enzyme (Figure EcAII_3eca). Structure of Class 1 type I enzymes is exemplified by EcAI [10] (Existing Figure), whereas Class 2 type III enzymes may be represented by EcAIII [11, 12] (Figure EcAIII_2zal). Class 2 L-asparaginases belong to the family of Ntn-hydrolases, which are expressed as inactive precursors that must undergo autoproteolytic cleavage into α and β subunits to achieve maturation [13]. While the existence of an alien type of ASNase in the symbiotic nitrogen-fixing bacterium Rhizobium etli had been recognized long ago [14], the structure of the inducible and thermolabile prototype Class 3 ReAV was solved and deposited in the PDB only recently [15] (Figure ReAV_7os5), followed by structures of the constitutive and thermostable isoform ReAIV [16]. More than 200 structures of ASNases have been deposited in the Protein Data Bank (PDB) by April 2024 [17] (Wlodawer et al., 2024). | ||
==Dependable Structures== | ==Dependable Structures== | ||
Revision as of 11:21, 11 July 2024
| |||||||||||
Proteopedia Page Contributors and Editors (what is this?)
This page complements a publication in scientific journals and is one of the Proteopedia's Interactive 3D Complement pages. For aditional details please see I3DC.
