In the central nervous system, the flavoprotein D-amino acid oxidase is responsible for catabolizing D-serine, the main endogenous coagonist of N-methyl-D-aspartate receptor. Dysregulation of D-serine brain levels in humans has been associated with neurodegenerative and psychiatric disorders. This D-amino acid is synthesized by the enzyme serine racemase, starting from the corresponding L-enantiomer, and degraded by both serine racemase (via an elimination reaction) and the flavoenzyme D-amino acid oxidase. To shed light on the role of human D-amino acid oxidase (hDAAO) in D-serine metabolism, the structural/functional relationships of this enzyme have been investigated in depth and several strategies aimed at controlling the enzymatic activity have been identified. Here, we focused on the effect of post-translational modifications: by using a combination of structural analyses, biochemical methods, and cellular studies, we investigated whether hDAAO is subjected to nitrosylation, sulfhydration, and phosphorylation. hDAAO is S-nitrosylated and this negatively affects its activity. In contrast, the hydrogen sulfide donor NaHS seems to alter the enzyme conformation, stabilizing a species with higher affinity for the flavin adenine dinucleotide cofactor and thus positively affecting enzymatic activity. Moreover, hDAAO is phosphorylated in cerebellum; however, the protein kinase involved is still unknown. Taken together, these findings indicate that D-serine levels can be also modulated by post-translational modifications of hDAAO as also known for the D-serine synthetic enzyme serine racemase.
Olaparib, an orally active inhibitor of poly(ADP-ribose)polymerase(PARP), is the drug of choice in the treatment of gBRCA1/2+ metastatic breast cancers. Unfortunately, Olaparib is poorly soluble with low bioavailability and tumor accumulation; nano-delivery could be a good choice to overcome these disadvantages. Here, a rapid and robust HPLC-ESI–MS/MS method for the quantification of Olaparib in ferritin nano-carriers led to the development of cells compartments, different tissues, plasma and urines and were validated to assess the effects of nano-delivery on cell compartment distribution of the drug. This method allows the quantification of Olaparib within the linear range of 0.1–10ng/mL in cells culture medium and cell cytoplasm, of 0.5–10ng/mL in nuclei, of 0.5–100ng/mL in plasma and urine and of 10–500ng/mL in tissue samples (kidney and liver). The limit of quantification was found to be 1.54 ng/mL for liver, 2.87 ng/mL for kidney, and lower than 0.48 ng/mL for all matrices. The method has been applied to quantify Ola encapsulated in ferritin-nano-carriers during the nano-drug development. The application of the method to human BRCA-mutated cell model to quantify the Olaparib distribution after incubation of free or ferritin-encapsulated Olaparib is also reported. This sensitive method allows the quantification of low concentrations of Olaparib released from nano-carriers in different cell compartments, leading to the determination of the drug release and kinetic profile of an essential parameter to validate nano-carriers.
5′-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an enzyme that regulates cellular energy homeostasis, glucose, fatty acid uptake, and oxidation at low cellular ATP levels. AMPK plays an important role in several molecular mechanisms and physiological conditions. It has been shown that AMPK can be dysregulated in different chronic diseases, such as inflammation, diabetes, obesity, and cancer. Due to its fundamental role in physiological and pathological cellular processes, AMPK is considered one of the most important targets for treating different diseases. Over decades, different AMPK targeting compounds have been discovered, starting from those that activate AMPK indirectly by altering intracellular AMP:ATP ratio to compounds that activate AMPK directly by binding to its activation sites. However, indirect altering of intracellular AMP:ATP ratio influences different cellular processes and induces side effects. Direct AMPK activators showed more promising results in eliminating side effects as well as the possibility to engineer drugs for specific AMPK isoforms activation. In this review, we discuss AMPK targeting drugs, especially concentrating on those compounds that activate AMPK by mimicking AMP. These compounds are poorly described in the literature and still, a lot of questions remain unanswered about the exact mechanism of AMP regulation. Future investigation of the mechanism of AMP binding will make it possible to develop new compounds that, in combination with others, can activate AMPK in a synergistic manner.
Monoacylglycerol lipase (MAGL) is a serine hydrolase that has a key regulatory role in controlling the levels of 2-arachidonoylglycerol (2-AG), the main signaling molecule in the endocannabinoid system. Identification of selective modulators of MAGL enables both to provide new tools for investigating pathophysiological roles of 2-AG, and to discover new lead compounds for drug design. The development of sensitive and reliable methods is crucial to evaluate this modulatory activity. In the current study, we report readily synthesized long-wavelength putative fluorogenic substrates with different acylic side chains to find a new probe for MAGL activity. 7-Hydroxyresorufinyl octanoate proved to be the best substrate thanks to the highest rate of hydrolysis and the best Km and Vmax values. In addition, in silico evaluation of substrates interaction with the active site of MAGL confirms octanoate resorufine derivative as the molecule of choice. The well-known MAGL inhibitors URB602 and methyl arachidonylfluorophosphonate (MAFP) were used for the assay validation. The assay was highly reproducible with an overall average Z′ value of 0.86. The fast, sensitive and accurate method described in this study is suitable for low-cost high-throughput screening (HTS) of MAGL modulators and is a powerful new tool for studying MAGL activity.
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