1
|
Sharma V, Fedoseyenko D, Joshi S, Abdelwahed S, Begley TP. Phosphomethylpyrimidine Synthase (ThiC): Trapping of Five Intermediates Provides Mechanistic Insights on a Complex Radical Cascade Reaction in Thiamin Biosynthesis. ACS CENTRAL SCIENCE 2024; 10:988-1000. [PMID: 38799670 PMCID: PMC11117688 DOI: 10.1021/acscentsci.4c00125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/26/2024] [Accepted: 03/26/2024] [Indexed: 05/29/2024]
Abstract
Phosphomethylpyrimidine synthase (ThiC) catalyzes the conversion of AIR to the thiamin pyrimidine HMP-P. This reaction is the most complex enzyme-catalyzed radical cascade identified to date, and the detailed mechanism has remained elusive. In this paper, we describe the trapping of five new intermediates that provide snapshots of the ThiC reaction coordinate and enable the formulation of a revised mechanism for the ThiC-catalyzed reaction.
Collapse
Affiliation(s)
- Vishav Sharma
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Dmytro Fedoseyenko
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Sumedh Joshi
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Sameh Abdelwahed
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Tadhg P. Begley
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| |
Collapse
|
2
|
De Vitto H, Belfon KKJ, Sharma N, Toay S, Abendroth J, Dranow DM, Lukacs CM, Choi R, Udell HS, Willis S, Barrera G, Beyer O, Li TD, Hicks KA, Torelli AT, French JB. Characterization of an Acinetobacter baumannii Monofunctional Phosphomethylpyrimidine Kinase That Is Inhibited by Pyridoxal Phosphate. Biochemistry 2024. [PMID: 38306231 DOI: 10.1021/acs.biochem.3c00640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2024]
Abstract
Thiamin and its phosphate derivatives are ubiquitous molecules involved as essential cofactors in many cellular processes. The de novo biosynthesis of thiamin employs the parallel synthesis of 4-methyl-5-(2-hydroxyethyl)thiazole (THZ-P) and 4-amino-2-methyl-5(diphosphooxymethyl) pyrimidine (HMP) pyrophosphate (HMP-PP), which are coupled to generate thiamin phosphate. Most organisms that can biosynthesize thiamin employ a kinase (HMPK or ThiD) to generate HMP-PP. In nearly all cases, this enzyme is bifunctional and can also salvage free HMP, producing HMP-P, the monophosphate precursor of HMP-PP. Here we present high-resolution crystal structures of an HMPK from Acinetobacter baumannii (AbHMPK), both unliganded and with pyridoxal 5-phosphate (PLP) noncovalently bound. Despite the similarity between HMPK and pyridoxal kinase enzymes, our kinetics analysis indicates that AbHMPK accepts HMP exclusively as a substrate and cannot turn over pyridoxal, pyridoxamine, or pyridoxine nor does it display phosphatase activity. PLP does, however, act as a weak inhibitor of AbHMPK with an IC50 of 768 μM. Surprisingly, unlike other HMPKs, AbHMPK catalyzes only the phosphorylation of HMP and does not generate the diphosphate HMP-PP. This suggests that an additional kinase is present in A. baumannii, or an alternative mechanism is in operation to complete the biosynthesis of thiamin.
Collapse
Affiliation(s)
- Humberto De Vitto
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, United States
| | - Kafi K J Belfon
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11790, United States
| | - Nandini Sharma
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, United States
| | - Sarah Toay
- Department of Biological Chemistry, Grinnell College, Grinnell, Iowa 50112, United States
| | - Jan Abendroth
- UCB BioSciences, Bainbridge Island, Washington 98110, United States
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington 98104, United States
| | - David M Dranow
- UCB BioSciences, Bainbridge Island, Washington 98110, United States
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington 98104, United States
| | - Christine M Lukacs
- UCB BioSciences, Bainbridge Island, Washington 98110, United States
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington 98104, United States
| | - Ryan Choi
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington 98104, United States
| | - Hannah S Udell
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, Washington 98104, United States
| | - Sydney Willis
- Department of Chemistry, Rollins College, Winter Park, Florida 32789, United States
| | - George Barrera
- Department of Chemistry and Biochemistry, Weber State University, Ogden, Utah 84408, United States
| | - Olive Beyer
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250, United States
| | - Teng Da Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11790, United States
| | - Katherine A Hicks
- Chemistry Department, State University of New York at Cortland, Cortland, New York 13045, United States
| | - Andrew T Torelli
- Department of Chemistry, Ithaca College, Ithaca, New York 14850, United States
| | - Jarrod B French
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, United States
| |
Collapse
|