Evidence that S-formylglutathione hydrolase and esterase D polymorphisms are identical

Metabolic Shades of S-D-Lactoylglutathione

S-D-lactoylglutathione (SDL) is an intermediate of the glutathione-dependent metabolism of methylglyoxal (MGO) by glyoxalases. MGO is an electrophilic compound that is inevitably produced in conjunction with glucose breakdown and is essentially metabolized via the glyoxalase route. In the last decades, MGO metabolism and its cytotoxic effects have been under active investigation, while almost nothing is known about SDL. This article seeks to fill the gap by presenting an overview of the chemistry, biochemistry, physiological role and clinical importance of SDL. The effects of intracellular SDL are investigated in three main directions: as a substrate for post-translational protein modifications, as a reservoir for mitochondrial reduced glutathione and as an energy currency. In essence, all three approaches point to one direction, namely, a metabolism-related regulatory role, enhancing the cellular defense against insults. It is also suggested that an increased plasma concentration of SDL or its metabolites may possibly serve as marker molecules in hemolytic states, particularly when the cause of hemolysis is a disturbance of the pay-off phase of the glycolytic chain. Finally, SDL could also represent a useful marker in such metabolic disorders as diabetes mellitus or ketotic states, in which its formation is expected to be enhanced. Despite the lack of clear-cut evidence underlying the clinical and experimental findings, the investigation of SDL metabolism is a promising field of research.

Activation of Esterase D by FPD5 Inhibits Growth of A549 Lung Cancer Cells via JAB1/p53 Pathway

Esterase D (ESD) is widely distributed in mammals, and it plays an important role in drug metabolism, detoxification, and biomarkers and is closely related to the development of tumors. In our previous work, we found that a chemical small-molecule fluorescent pyrazoline derivative, FPD5, an ESD activator, could inhibit tumor growth by activating ESD, but its molecular mechanism is still unclear. Here, by using RNA interference (RNAi), andco-immunoprecipitation techniques, we found that ESD suppressed the nucleus exportation of p53 through reducing the interaction between p53 and JAB1. The protein level of p53 in the nucleus was upregulated and the downstream targets of p53 were found by Human Gene Expression Array. p53 inhibited the expression of CDCA8 and CDC20. Lastly, the cell cycle of A549 cells was arrested at the G0/G1 phase. Together, our data suggest that ESD inhibited the cancer cell growth by arresting the cell cycle of A549 cells via the JAB1/p53 signaling pathway. Our findings provide a new insight into how to inhibit the growth of lung cancer with the activation of ESD by FPD5.

Regulation of S-formylglutathione hydrolase by the anti-aging gene klotho

Klotho is an aging-suppressor gene. The purpose of this study is to investigate the binding sites (receptors) and function of short-form Klotho (Skl). We showed that Skl physically bound to multiple proteins. We found physical and functional interactions between Skl and S-formylglutathione hydrolase (FGH), a key enzyme in the generation of the major cellular anti-oxidant GSH, using co-immunoprecipitation-coupled mass spectrometry. We further confirmed the colocalization of Skl and FGH around the nucleus in kidney cells using immunofluorescent staining. Skl positively regulated FGH gene expression via Kid3 transcription factor. Overexpression of Skl increased FGH mRNA and protein expression while silencing of Skl attenuated FGH mRNA and protein expression. Klotho gene mutation suppressed FGH expression in red blood cells and kidneys resulting in anemia and kidney damage in mice. Overexpression of Skl increased total GSH production and the GSH/GSSG ratio, an index of anti-oxidant capacity, leading to a decrease in intracellular H₂O₂ and superoxide levels. The antioxidant activity of Skl was eliminated by silencing of FGH, indicating that Skl increased GSH via FGH. Interestingly, Skl directly interacted with FGH and regulated its function. Site-directed mutagenesis of the N-glycan-modified residues in Skl abolished its antioxidant activity, suggesting that these N-glycan moieties are important features that interact with FGH. Specific mutation of Asp to Ala at site 285 resulted in a loss of anti-oxidant activity of Skl, suggesting that N-glycosylation at site 285 is the key mechanism that determines Skl activity. Therefore, this study demonstrates, for the first time, that Skl regulates anti-oxidant GSH generation via interaction with FGH through N-glycosylation.

The structure of a putative S-formylglutathione hydrolase from Agrobacterium tumefaciens

The structure of the Atu1476 protein from Agrobacterium tumefaciens was determined at 2 A resolution. The crystal structure and biochemical characterization of this enzyme support the conclusion that this protein is an S-formylglutathione hydrolase (AtuSFGH). The three-dimensional structure of AtuSFGH contains the alpha/beta hydrolase fold topology and exists as a homo-dimer. Contacts between the two monomers in the dimer are formed both by hydrogen bonds and salt bridges. Biochemical characterization reveals that AtuSFGH hydrolyzes C--O bonds with high affinity toward short to medium chain esters, unlike the other known SFGHs which have greater affinity toward shorter chained esters. A potential role for Cys54 in regulation of enzyme activity through S-glutathionylation is also proposed.

Identification of human esterase D subunits from the homodimeric and heterodimeric forms of five phenotypes by a new two-dimensional isoelectric focusing method

A new two-dimensional isoelectric focusing method was developed to identify the human esterase D (EsD) subunits from the homodimeric and heterodimeric forms of five EsD phenotypes. EsD polymorphism was also analyzed by one-dimensional isoelectric focusing under reducing and mild denaturing conditions to study the influence of dithiothreitol and low concentrations of urea on the focusing pattern of the EsD dimers.

Purification and characterization of esterases D-1 and D-2 from human erythrocytes

Esterase D-1 (carboxylesterase; carboxylic-ester hydrolase, EC 3.1.1.1) was purified to homogeneity and esterase D-2 was highly purified from human erythrocytes. A new procedure, which included fractionation with ammonium sulfate, hydrophobic chromatography on a Toyopearl HW-65 column, and chromatographies on CM-cellulose and hydroxylapatite columns, was developed. Esterases D-1 and D-2 were purified about 9000- and 5600-fold over the precipitates with 65% saturated ammonium sulfate in 14 and 35% yields, respectively. The minimum molecular weights of esterases D-1 and D-2 were estimated to be 35,000 based on the mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with or without 2-mercaptoethanol. The molecular weights of both enzymes were calculated to be 76,000 by gel filtration. These findings indicated that these two enzymes consisted of dimer without an intermolecular disulfide bond(s). Amino acid analysis of esterase D-1 showed that the total residues of aspartic acid plus asparagine, glutamic acid plus glutamine, glycine, and leucine represent about 40% of the total amino acid residues. Esterases D-1 and D-2 have almost identical biochemical characteristics, including Km values, sensitivities to sulfhydryl reagents, and molecular weights. Esterase D-2 cross-reacted with a rabbit antibody raised against the purified esterase D-1.