title: Poly(aspartic acid) (PAA) hydrolases and PAA biodegradation: current knowledge and impact on applications.
abstract: Thermally synthesized poly(aspartic acid) (tPAA) is a bio-based, biocompatible, biodegradable, and water-soluble polymer that has a high proportion of β-Asp units and equivalent moles of D- and L-Asp units. Poly(aspartic acid) (PAA) hydrolase-1 and hydrolase-2 are tPAA biodegradation enzymes purified from Gram-negative bacteria. PAA hydrolase-1 selectively cleaves amide bonds between β-Asp units via an endo-type process, whereas PAA hydrolase-2 catalyzes the exo-type hydrolysis of the products of tPAA hydrolysis by PAA hydrolase-1. The novel reactivity of PAA hydrolase-1 makes it a good candidate for a biocatalyst in β-peptide synthesis. This mini-review gives an overview of PAA hydrolases with emphasis on their biochemical and functional properties, in particular, PAA hydrolase-1. Functionally related enzymes, such as poly(R-3-hydroxybutyrate) depolymerases and β-aminopeptidases, are compared to PAA hydrolases. This mini-review also provides findings that offer an insight into the catalytic mechanisms of PAA hydrolase-1 from Pedobacter sp. KP-2.
authors.affiliation: Bioengineering Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan. thiraish@riken.jp.|Bioplastic Research Team, Biomass Engineering Research Division, RIKEN Center for Sustainable Resource Science (CSRS), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan. thiraish@riken.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hiraishi
mesh_terms: D001224:Aspartic Acid / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism*; D001711:Biotransformation; D006868:Hydrolysis; D060485:Pedobacter / Q000201:enzymology*; D012697:Serine Endopeptidases / Q000378:metabolism*
chemical_list: D001704:Biopolymers; C499773:alpha,beta-poly(aspartic acid); D001224:Aspartic Acid; D012697:Serine Endopeptidases; C473051:poly(aspartic acid) hydrolase
keywords: Enzyme-catalyzed polymerization; Poly(aspartic acid); Poly(aspartic acid) hydrolase; Stereoselectivity; β-Amide linkage