Adenosine kinase mediates high affinity adenosine salvage in Trypanosoma brucei.

Publisher: Elsevier Inc. on behalf of American Society for Biochemistry and Molecular Biology Country of Publication: United States NLM ID: 2985121R Publication Model: Print-Electronic Cited Medium: Print ISSN: 0021-9258 (Print) Linking ISSN: 00219258 NLM ISO Abbreviation: J Biol Chem Subsets: MEDLINE

Publication: 2021- : [New York, NY] : Elsevier Inc. on behalf of American Society for Biochemistry and Molecular Biology
Original Publication: Baltimore, MD : American Society for Biochemistry and Molecular Biology

Adenine/*chemistry ; Adenosine Kinase/*chemistry ; Antimetabolites/*chemistry ; Protozoan Proteins/*chemistry ; Trypanosoma brucei brucei/*enzymology ; Vidarabine/*chemistry; Adenine/metabolism ; Adenosine Kinase/antagonists & inhibitors ; Adenosine Kinase/genetics ; Adenosine Kinase/metabolism ; Animals ; Antimetabolites/therapeutic use ; Catalysis ; Guanosine Triphosphate/chemistry ; Guanosine Triphosphate/metabolism ; Humans ; Leishmania donovani/enzymology ; Leishmania donovani/genetics ; Membrane Transport Proteins/metabolism ; Protozoan Proteins/antagonists & inhibitors ; Protozoan Proteins/genetics ; Protozoan Proteins/metabolism ; Recombinant Proteins/antagonists & inhibitors ; Recombinant Proteins/chemistry ; Recombinant Proteins/genetics ; Recombinant Proteins/metabolism ; Substrate Specificity/physiology ; Trypanosoma brucei brucei/genetics ; Trypanosomiasis, African/drug therapy ; Trypanosomiasis, African/enzymology ; Trypanosomiasis, African/genetics ; Vidarabine/therapeutic use

African sleeping sickness is caused by Trypanosoma brucei. This extracellular parasite lacks de novo purine biosynthesis, and it is therefore dependent on exogenous purines such as adenosine that is taken up from the blood and other body fluids by high affinity transporters. The general belief is that adenosine needs to be cleaved to adenine inside the parasites in order to be used for purine nucleotide synthesis. We have found that T. brucei also can salvage this nucleoside by adenosine kinase (AK), which has a higher affinity to adenosine than the cleavage-dependent pathway. The recombinant T. brucei AK (TbAK) preferably used ATP or GTP to phosphorylate both natural and synthetic nucleosides in the following order of catalytic efficiencies: adenosine > cordycepin > deoxyadenosine > adenine arabinoside (Ara-A) > inosine > fludarabine (F-Ara-A). TbAK differed from the AK of the related intracellular parasite Leishmania donovani by having a high affinity to adenosine (K m = 0.04-0.08 microm depending on [phosphate]) and by being negatively regulated by adenosine (K i = 8-14 microm). These properties make the enzyme functionally related to the mammalian AKs, although a phylogenetic analysis grouped it together with the L. donovani enzyme. The combination of a high affinity AK and efficient adenosine transporters yields a strong salvage system in T. brucei, a potential Achilles' heel making the parasites more sensitive than mammalian cells to adenosine analogs such as Ara-A. Studies of wild-type and AK knockdown trypanosomes showed that Ara-A inhibited parasite proliferation and survival in an AK-dependent manner by affecting nucleotide levels and by inhibiting nucleic acid biosynthesis.

0 (Antimetabolites)
0 (Membrane Transport Proteins)
0 (Protozoan Proteins)
0 (Recombinant Proteins)
86-01-1 (Guanosine Triphosphate)
EC 2.7.1.20 (Adenosine Kinase)
FA2DM6879K (Vidarabine)
JAC85A2161 (Adenine)

Date Created: 20080103 Date Completed: 20080415 Latest Revision: 20210206

20231215

10.1074/jbc.M705603200

18167353