Detailed mechanism of catalysis by tetrameric L-glutaminase-asparaginase from Pseudomonas 7A (PGA)

Conference: 2022: 72nd ACA Annual Meeting
Pawel Strzelczyk Poster Author
Center for Structural Biology, Center for Cancer Research, National Cancer Institute
Frederick, MD 
 
Di Zhang Additional Author
Center for Structural Biology, Center for Cancer Research, National Cancer Institute
MD 
 
Marzena Dyba Additional Author
Center for Structural Biology, Center for Cancer Research, National Cancer Institute
MD 
 
Alexander Wlodawer Additional Author
Center for Structural Biology, Center for Cancer Research, National Cancer Institute
 
Jacek Lubkowski Additional Author
Center for Structural Biology, Center for Cancer Research, National Cancer Institute
MD 
 
07/31/2022: 5:30 PM - 7:30 PM
Poster Session 
Portland Marriott Downtown Waterfront 
Room: Exhibit Hall 

Description

L-asparaginases (EC 3.5.1.1) are widely distributed enzymes among both bacterial and eukaryotic organisms. For over 40 years, L-asparaginases have played a critical role in the treatment of juvenile leukemias and lymphomas. Their primary biochemical function is to catalyze the hydrolysis of L-Asn to L-Asp. Most L-asparaginases also catalyze the hydrolysis of L-Gln to L-Glu, and those that exhibit glutaminase activity that is comparable or higher than asparaginase activity are often referred to as glutaminases-asparaginases. Based on extensive structural and functional studies of L-glutaminase-asparaginase from Pseudomonas 7A (PGA), we were able to show unequivocally that the reaction catalyzed by this enzyme proceeds through formation of a covalent intermediate and utilizes a common ping-pong catalytic mechanism consisting of two subsequent nucleophilic substitutions, as previously observed for EcAII. Additionally, by confirming that the same mechanism applies to L-Asn and L-Gln, we postulate that it is common for all these structurally related enzymes. Detailed structural studies of PGA and its complexes with substrates should create a foundation for rational development of L-asparaginases with modulated relative activities vs. L-Asn or L-Gln, which may be beneficial toward the development of improved anti-leukemia therapeutics.