Expression of glyoxalase I and II in normal and breast cancer tissues

The binding of iron and zinc to glyoxalase II occurs exclusively as di-metal centers and is unique within the metallo-beta-lactamase family

Cytosolic glyoxalase 2 (GLX2-2) from Arabidopsis thaliana is a metalloenzyme that has been shown to bind a mixture of Zn, Fe, or Mn when produced in cells grown in rich media. In an effort to prepare metal-enriched samples, GLX2-2 was over-expressed in minimal media containing either Zn, Fe, or Mn. The resulting enzymes bound an average of 1 equivalent of metal ion and were partially enriched with a specific metal ion. The enzymes produced in minimal media were active towards the substrate S-D-lactoylglutathione, yielding kcat/ Km values similar to those of rich media GLX2-2. EPR studies on minimal media GLX2-2 samples revealed spectra which were identical to those over-expressed in rich media that contained nearly 2 equivalents of metal. The EPR spectra showed the presence of antiferromagnetically and ferromagnetically coupled, dinuclear metal centers. EXAFS spectra on the minimal media GLX2-2 samples over-expressed in the presence of Fe or Zn were also very similar to those of the rich media GLX2-2 samples, indicating the presence of dinuclear metal centers. The EXAFS studies also demonstrate that Zn(II) and Fe (in the Fe-enriched sample) are distributed in the dinuclear site. These data indicate that the minimal media GLX2-2 samples are a mixture of fully loaded, dinuclear metal-containing enzyme and metal-free enzyme. This characteristic of A. thaliana GLX2-2 makes it unique among the other members of the metallo-beta-lactamase family in that it does not ever appear to exist as a mononuclear metal ion containing enzyme and that it exhibits positive cooperativity in metal binding.

Bovine mammary gene expression profiling using a cDNA microarray enhanced for mammary-specific transcripts

A cDNA microarray resource enhanced for transcripts specific to the bovine mammary gland (BMAM) has been developed and used in pilot studies to examine gene expression profiles in the mammary gland. One goal driving development of this resource was to shed some light on the pathways and mechanisms specifically related to bovine mammary gland growth and development. To accomplish this, gene expression patterns from bovine adipose, liver, adrenal, lymph, spleen, thymus, gut, and developing mammary tissue were compared using the BMAM microarray. We have thus identified a putative set of 16 genes being preferentially expressed in developing mammary gland. Another of our long-term goals is to elucidate the genes and pathways associated with bovine lactation and involution and to use these as a model for human mammary gland development as it relates to human breast cancer risks. To begin this process, we conducted a pilot study, comparing gene expression profiles of lactating bovine mammary tissue against nonlactating tissue on the BMAM microarray. Our results have yielded many novel and interesting genes exhibiting differential expression in lactating mammary tissue, including oncogenes (VAV3, C-myc), mediators of apoptosis (Caspase 8), and cell cycle regulators (LASP1).

Scavenging system efficiency is crucial for cell resistance to ROS-mediated methylglyoxal injury

Methylglyoxal is a reactive dicarbonyl compound endogenously produced mainly from glycolytic intermediates. Recent research indicates that methylglyoxal is a potent growth inhibitor and genotoxic agent. The antiproliferative activity of methylglyoxal has been investigated for pharmacological application in cancer chemotherapy. However, various cells are not equally sensitive to methylglyoxal toxicity. Therefore, it would be important to establish the cellular factors responsible for the different cell-type specific response to methylglyoxal injury, in order to avoid the risk of failure of a therapy based on increasing the intracellular level of methylglyoxal. To this purpose, we comparatively evaluated the signaling transduction pathway elicited by methylglyoxal in human glioblastoma (ADF) and neuroblastoma (SH-SY 5Y) cells. Results show that methylglyoxal causes early and extensive reactive oxygen species generation in both cell lines. However, SH-SY 5Y cells show higher sensitivity to methylglyoxal challenge due to a defective antioxidant and detoxifying ability that, preventing these cells from an efficient scavenging action, elicits extensive caspase-9 dependent apoptosis. These data emphasize the pivotal role of antioxidant and detoxifying systems in determining the grade of sensitivity of cells to methylglyoxal.

Flexible Metal Binding of the Metallo-β-lactamase Domain: Glyoxalase II Incorporates Iron, Manganese, and Zinc in Vivo†

Glyoxalase II belongs to the metallo-beta-lactamase superfamily of proteins, possessing the characteristic dinuclear active site. Within this protein family, glyoxalase II from Arabidopsis thaliana is the first member to be isolated with significant amounts of iron, manganese, and zinc when being recombinantly produced in Escherichia coli. Enzyme preparations with different ratios of these three metals all yield k(cat)/K(M) values in the range of 1.5-1.9 s(-1) microM(-1) with the substrate S-d-lactoylglutathione. X-ray absorption spectroscopy reveals binding of all three metals to the dinuclear active site with 5-6-fold coordination consisting of 2.5 +/- 0.5 histidine and 2.5 +/- 0.5 oxygen ligands. This model does not distinguish site-specific or distributed binding. The metal-metal distance is determined to be 3.18 +/- 0.06 A. Electron paramagnetic resonance spectroscopy gives evidence for several different types of dimetal sites, including spin-coupled Fe(III)Fe(II), Fe(III)Zn(II), and Mn(II)Mn(II) centers. The metal-ligand distances measured by X-ray absorption spectroscopy vary depending on the metal type and comply with their element-specific, characteristic values. This reflects a high degree of structural flexibility within the glyoxalase II dinuclear active site, which is considered as the structural basis for its broad metal selectivity.

Differing expression of enzymes of the glyoxalase system in superficial and invasive bladder carcinomas

This work aimed to study the activities of the glyoxalase system enzymes (glyoxalase I (GI) and glyoxalase II (GII) and their gene expression in human bladder carcinomas compared with the corresponding normal mucosa. Samples of these tissues were collected from 26 patients with superficial (SBC) or invasive bladder cancer (IBC) and used to evaluate enzyme activity and gene expression by northern blot analysis. In keeping with the electrophoretic pattern and the expression level of the respective genes, GI activity significantly increased in SBC samples, while it remained unchanged in IBC samples compared with the normal mucosa. In contrast, GII showed a higher activity in the tumour (either SBC or IBC samples) versus normal tissues. These results confirm the role of the glyoxalases in detoxifying cytotoxic methylglyoxal (MG) in bladder cancer. The differing levels of GI activity level and gene expression of GI between the SBC and IBC samples could help in their differential diagnosis.

Tumor necrosis factor-induced modulation of glyoxalase I activities through phosphorylation by PKA results in cell death and is accompanied by the formation of a specific methylglyoxal-derived AGE

Tumor necrosis factor (TNF)-induced cell death in the fibrosarcoma cell line L929 is a caspase-independent process that is characterized by increased production of reactive oxygen species (ROS) in the mitochondria. To elucidate this ROS-dependent cell death pathway, a comparative study of the phosphoproteins present in TNF-treated and control cells was performed. Here we report that TNF induces an increased phosphorylation of glyoxalase I that is mediated by protein kinase A and required for cell death. We also show that TNF induces a substantial increase in intracellular levels of methylglyoxal (MG) that leads to the formation of a specific MG-derived advanced glycation end product and that this formation occurs as a consequence of increased ROS production. These data indicate that MG modification of proteins is a targeted process and that MG may thus function as a signal molecule during the regulation of cell death. Furthermore, we provide evidence that the TNF-induced phosphorylation of glyoxalase I is not involved in detoxification of MG by means of the glyoxalase system, but that phosphorylated glyoxalase I is on the pathway leading to the formation of a specific MG-derived advanced glycation end product.