A Convenient, Rapid, Sensitive, and Reliable Spectrophotometric Assay for Adenylate Kinase Activity

Adenylate kinases of thermophiles Aquifex aeolicus and Geobacillus stearothermophilus: biochemical and kinetic studies

Adenylate kinases (AK) play a pivotal role in the regulation of cellular energy. The aim of our work was to achieve the overproduction and purification of AKs from two groups of bacteria and to determine, for the first time, the comprehensive biochemical and kinetic properties of adenylate kinase from Gram-negative Aquifex aeolicus (AK_aq) and Gram-positive Geobacillus stearothermophilus (AK_st). Therefore we determined K_M and V_max values, and the effects of temperature, pH, metal ions, donors of the phosphate groups and inhibitor Ap₅A for both thermophilic AKs. The kinetic studies indicate that both AKs exhibit significantly higher affinity for substrates with the pyrophosphate group than for adenosine monophosphate. AK activation by Mg²⁺ and Mn²⁺ revealed that both ions are efficient in the synthesis of adenosine diphosphate and adenosine triphosphate; however, Mn²⁺ ions at 0.2-2.0 mmol/L concentration were more efficient in the activation of the ATP synthesis than Mg²⁺ ions. Our research demonstrates that zinc ions inhibit the activity of enzymes in both directions, while Ap₅A at a concentration of 10 µmol/L and 50 µmol/L inhibited both enzymes with a different efficiency. Sigmoid-like kinetics were detected at high ATP concentrations not balanced by Mg²⁺, suggesting the allosteric effect of ATP for both bacterial AKs.

Identification of AK4 as a novel therapeutic target for serous ovarian cancer

The present study aimed to assess the expression level of adenylate kinase 4 (AK4) in human serous ovarian cancer (SOC) tissues and investigate the possible involvement of AK4 in SOC progression. Bioinformatics analysis based on The Cancer Genome Atlas (TCGA) database and immunohistochemical (IHC) assays were performed to assess the expression level of AK4 in human SOC tissues. Clinical pathological features of patients with SOC were also evaluated. Colony formation, MTT, wound healing and Transwell assays were conducted to investigate the effects of AK4 on the proliferation, migration, and invasion of SOC cells in vitro. Mouse xenograft and lung metastasis models were developed to evaluate the effects of AK4 on tumor growth and metastasis in vivo. High expression levels of AK4 were identified in human SOC tissues compared with in normal tissues according to TCGA database and the results of IHC assays. A contribution of AK4 to tumor growth and metastasis of SOC cells in vivo was also shown. The present study confirmed the involvement of AK4 in the progression of SOC, and the results indicated that AK4 could serve as a novel therapeutic target for SOC treatment.

Enzymes, Biocatalysis and Chemical Biology

Chemical transformations that take advantage of biocatalysis are of great interest to chemists [...].