Adenosine‐AMP exchange activity is an integral part of the mammalian adenosine kinase

Gupta, Radhey S.

doi:10.1080/15216549600201541

Cited by 5 publications

(2 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In characterizing purified AK from rat liver, Mimouni et al [59,60] discovered that when radioactive adenosine and non-labeled AMP were added to the enzyme, the result was formation of labeled AMP. This exchange reaction, which was dependent on the presence of ADP and Mg 2+ [59], was also seen with AK from other sources [61]. Although the exact mechanism of adenosine-AMP exchange activity is not clearly understood, it can be explained with the backward reaction of AK.…”

Section: Substrate Inhibition and Reaction Mechanism Of Akmentioning

confidence: 93%

Adenosine kinase and ribokinase – the RK family of proteins

Park

Gupta

2008

Cell. Mol. Life Sci.

123

142

View full text Add to dashboard Cite

Ribokinase (RK) and adenosine kinase (AK) catalyze the phosphorylation of ribose and adenosine to ribose-5-phosphate and AMP, respectively. Belonging to the RK family of proteins, these enzymes share a number of unique structural and functional elements. Extensive work has been carried out on many aspects of these enzymes in recent years, and we summarize the wealth of information currently available on them. The topics covered include descriptions of the primary and three-dimensional structures of AK and RK, their phylogenetic relationships, biochemical aspects of these enzymes including their reaction mechanisms and ionic requirements, and also work on certain inhibitors of these enzymes. The cellular metabolism and transport of ribose and adenosine are also briefly discussed, as well as the beneficial effects of ribose and adenosine in physiology and how these effects can be harnessed for pharmacological purposes.

show abstract

Section: Substrate Inhibition and Reaction Mechanism Of Akmentioning

confidence: 93%

Adenosine kinase and ribokinase – the RK family of proteins

Park

Gupta

2008

Cell. Mol. Life Sci.

123

142

View full text Add to dashboard Cite

show abstract

“…With human AK, the K m for methyl-Ado was 960 M, and the V max was 0.64 nmol/mgmin (Table 3), which are similar to the values seen for M. tuberculosis AK in the absence of KCl. P i has been reported to have a stimulatory effect on various AKs, with a concurrent depression of the K m for Ado and ATP and an increase in V max for these reactants (12,13,16,17). The effect of P i on M. tuberculosis AK was evaluated, using up to 50 mM sodium phosphate with Ado concentrations both above and below the K m for Ado, and little or no stimulation of activity was observed (data not shown).…”

Section: Purification Of M Tuberculosis Akmentioning

confidence: 99%

Identification and Characterization of a Unique Adenosine Kinase from Mycobacterium tuberculosis

2003

View full text Add to dashboard Cite

Adenosine kinase (AK) is a purine salvage enzyme that catalyzes the phosphorylation of adenosine to AMP. In Mycobacterium tuberculosis, AK can also catalyze the phosphorylation of the adenosine analog 2-methyladenosine (methyl-Ado), the first step in the metabolism of this compound to an active form. Purification of AK from M. tuberculosis yielded a 35-kDa protein that existed as a dimer in its native form. Adenosine (Ado) was preferred as a substrate at least 30-fold (K m ‫؍‬ 0.8 ؎ 0.08 M) over other natural nucleosides, and substrate inhibition was observed when Ado concentrations exceeded 5 M. M. tuberculosis and human AKs exhibited different affinities for methyl-Ado, with K m values of 79 and 960 M, respectively, indicating that differences exist between the substrate binding sites of these enzymes. ATP was a good phosphate donor (K m ‫؍‬ 1100 ؎ 140 M); however, the activity levels observed with dGTP and GTP were 4.7 and 2.5 times the levels observed with ATP, respectively. M. tuberculosis AK activity was dependent on Mg 2؉ , and activity was stimulated by potassium, as reflected by a decrease in the K m and an increase in V max for both Ado and methyl-Ado. The N-terminal amino acid sequence of the purified enzyme revealed complete identity with Rv2202c, a protein currently classified as a hypothetical sugar kinase. When an AK-deficient strain of M. tuberculosis (SRICK1) was transformed with this gene, it exhibited a 5,000-fold increase in AK activity compared to extracts from the original mutants. These results verified that the protein that we identified as AK was coded for by Rv2202c. AK is not commonly found in bacteria, and to the best of our knowledge, M. tuberculosis AK is the first bacterial AK to be characterized. The enzyme shows greater sequence homology with ribokinase and fructokinase than it does with other AKs. The multiple differences that exist between M. tuberculosis and human AKs may provide the molecular basis for the development of nucleoside analog compounds with selective activity against M. tuberculosis.

show abstract

Inhibition of adenosine kinase by phosphonate and bisphosphonate derivatives

2006

View full text Add to dashboard Cite

The enzyme adenosine kinase (AK) plays a central role in regulating the intracellular and interstitial concentration of the purine nucleoside adenosine (Ado). In view of the beneficial effects of Ado in protecting tissues from ischemia and other stresses, there is much interest in developing AK inhibitors, which can regulate Ado concentration in a site- and event-specific manner. The catalytic activity of AK from different sources is dependent upon the presence of activators such as phosphate (Pi). In this work we describe several new phosphorylated compounds which either activate or inhibit AK. The compounds acetyl phosphate, carbamoyl phosphate, dihydroxyacetone phosphate and imidodiphosphate were found to stimulate AK activity in a dose-dependent manner comparable to that seen with Pi. In contrast, a number of phosphonate and bisphosphonate derivatives, which included clodronate and etidronate, were found to inhibit the activity of purified AK in the presence of Pi. These AK inhibitors (viz. clodronate, etidronate, phosphonoacetic acid, 2-carboxyethylphosphonic acid, N-(phosphonomethyl)-glycine and N-(phosphonomethyl)iminodiacetic acid), at concentrations at which they inhibited AK, were also shown to inhibit the uptake of (3)H-adenosine and its incorporation into macromolecules in cultured mammalian cells, indicating that they were also inhibiting AK in intact cells. The drug concentrations at which these effects were observed showed limited toxicity to the cultured cells, indicating that these effects are not caused by cellular toxicity. These results indicate that the enzyme AK provides an additional cellular target for the clinically widely used bisphosphonates and related compounds, which could possibly be exploited for a new therapeutic application. Our structure-activity studies on different AK activators and inhibitors also indicate that all of the AK activating compounds have a higher partial positive charge (delta(+)) on the central phosphorous atom in comparison to the inhibitors. This information should prove helpful in the design and synthesis of more potent inhibitors of AK.

show abstract

Adenosine‐AMP exchange activity is an integral part of the mammalian adenosine kinase

Cited by 5 publications

References 7 publications

Adenosine kinase and ribokinase – the RK family of proteins

Adenosine kinase and ribokinase – the RK family of proteins

Identification and Characterization of a Unique Adenosine Kinase from Mycobacterium tuberculosis

Inhibition of adenosine kinase by phosphonate and bisphosphonate derivatives

Contact Info

Product

Resources

About