Synthesis and evaluation of general mechanism-based inhibitors of sulfatases based on (difluoro)methyl phenyl sulfate and cyclic phenyl sulfamate motifs

Several model mechanism-based inhibitors (MbIs) were designed and evaluated for their ability to inhibit sulfatases. The MbI motifs were based on simple aromatic sulfates, which are known to be commonly accepted substrates across this highly conserved enzyme class, so that they might be generally useful for sulfatase labeling studies. (Difluoro)methyl phenol sulfate analogs, constructed to release a reactive quinone methide trap, were not capable of irreversibly inactivating the sulfatase active site. On the other hand, the cyclic sulfamates (CySAs) demonstrated inhibition profiles consistent with an active site-directed mode of action. These molecules represent a novel scaffold for labeling sulfatases and for probing their catalytic mechanism.     

The selective estrogen enzyme modulator (SEEM) in breast cancer

Human breast cancer tissue contains all the enzymes (estrone sulfatase, 17β-hydroxysteroid dehydrogenase, aromatase) involved in the last steps of estradiol biosynthesis. This tissue also contains sulfotransferase for the formation of the biologically inactive estrogen sulfates. In the last years, it was demonstrated that various progestins (promegestone, nomegestrol acetate, medrogestone), as well as tibolone and its metabolites are potent inhibitors of sulfatase and 17β-hydroxysteroid dehydrogenase activities. It was also shown that medrogestone, nomegestrol acetate, promegestone or tibolone can stimulate the sulfotransferase activity for the local production of estrogen sulfates. All these data, in addition to numerous agents, which can block the aromatase action, lead to the new concept of selective estrogen enzyme modulators (SEEM), which can largely apply to breast cancer tissue. The exploration of various progestins and other active agents in trials with breast cancer patients, showing an inhibitory effect on sulfatase and 17β-hydroxysteroid dehydrogenase, or a stimulatory effect on sulfotransferase, will provide a new possibility in the treatment of this disease.     

Aryl sulfatase from Naja nigricolis venom: characterization and possible contribution in the pathology of snake poisoning

The venom of Naja nigricolis was found to contain a high level of the enzyme aryl sulfatase. The enzyme was isolated from the venom of N. nigriclois and purified to electrophoretic homogeneity by gel chromatography on Sephadex G-100, DEAE-cellulose, and phenyl-sepharose columns. The enzyme was optimally active at pH 5 and 40 degrees C. Arrhenius plot for the determination of the activation energy (E(a)) gave the value 25 kJ/mol with a half-life (t(1/2)) of 5 min at 50 degrees C. It was highly activated by Fe(2+) and Ca(2+) and inhibited by Co(2+) and Mn(2+). The enzyme catalyzed the hydrolysis of the fluorescent compound methylumbelliferyl-sulfate (MU-SO(4)). Double reciprocal plots of initial velocity data, using MU-SO(4) as substrate, gave a K(M) value of 110 microM and V(max) of 225 micromol min(-1) x mg(-1). N. nigricolis Aryl sulphatase also hydrolyzed chondroitin-4-sulphate. It was inhibited competitively by N-acetyl glucosamine sulfate (GlcNAc-SO(4)), glucose-6-sulfate (Glc-6-SO(4)), and glucose 1-sulfate (Glc-1-SO(4)). Extrapolated inhibition binding constants (K(i)) gave the values of 3, 25, and 315 microM for GlcNAc-SO(4), Glc-6-SO(4), and Glc-1-SO(4) respectively.     

Role of steroid sulfatase in local formation of estrogen in post-menopausal breast cancer patients

More than two-thirds of breast cancers occur in post-menopausal women, and depend on the estrogens for their proliferation and survival. For the treatment of estrogen-dependent breast cancers, two major treatment options are now available. One is selective estrogen receptor modulator (SERM) such as Tamoxifen and another is aromatase inhibitor such as Anastrozole, Letrozole and Exemestane, which reduce local in situ formation of estrogens. Although these therapies are clinically active for advanced and early breast cancers, de novo and/or acquired resistance to SERM and/or aromatase inhibitors are also clinical problem. Recent studies suggest that local formation of estrogens in the breast tumors is more important than circulating estrogen in plasma for the growth and survival of estrogen-dependent breast cancer in post-menopausal women. The rationale for the importance of local formation of estrogens is based on the following evidences. Estradiol (E2) levels in breast tumors are equivalent to those of pre-menopausal patients, although plasma E2 levels are 50-fold lower after menopause. E2 concentrations in breast tumors of post-menopausal women are 10–40 times higher than serum level. Biosynthesis of estrogens in breast tumors tissues occurs via two major different routes, one is aromatase pathway and another is steroid-sulfatase (STS) pathway. Whereas many studies has been reported about aromatase inhibitor and its clinical trial results in breast cancer patients, limited information are available regarding to other estrogen regulating enzymes including STS, its role in breast tumors and STS inhibitors. STS is the enzyme that hydrolyses estrone 3-sulfate (E₁S) and dehydroepiandrosterone-sulfate (DHEA-S) to their active un-sulfoconjugated forms, thereby stimulating the growth and survival of estrogen-dependent breast tumors. It has been well known that E₁S level are much higher than E2 level both in plasma and tumor of post-menopausal patients. Recent reports show that more than 80% of breast tumors are stained with anti-STS antibody and the expression of STS is an independent prognostic factor in breast cancer. Taking these findings into consideration, local formation of estrogens could be partially synthesized from large amount of E₁S by STS, which exist in breast cancer. On the other hand, aromatase localizes in stroma and adipocyte surrounding breast cancer. Furthermore, since estrogen formation from E₁S and DHEA-S (STS pathway) cannot be blocked by aromatase inhibitors, STS is thought to be a new molecular target for the treatment of estrogen-dependent tumor post-SERM and/or aromatase inhibitors. In this symposium, these recent rationale for the importance of STS in post-menopausal breast cancer patients is reviewed as well as STS inhibitor.     

Mass spectrometry analysis of the human endosulfatase Hsulf-2

The human 6-O-endosulfatases HSulf-1 and -2 catalyze the region-selective hydrolysis of the 6-O-sulfate group of the glucosamine residues within sulfated domains of heparan sulfate, thereby ensuring a unique and original post-biosynthetic modification of the cell surface proteoglycans. While numerous studies point out the role of HSulf-2 in crucial physiological processes as well as in pathological conditions particularly in cancer, its structural organization in two chains and its functional properties remain poorly understood. In this study, we report the first characterization by mass spectrometry (MS) of HSulf-2. An average molecular weight of 133,115 Da was determined for the whole enzyme by MALDI-TOF MS, i.e. higher than the naked amino acid backbone (98,170 Da), highlighting a significant contribution of post-translational modifications. The HSulf-2 protein sequence was determined by Nano-LC-MS/MS, leading to 63% coverage and indicating at least four N-glycosylation sites at Asn 108, 147, 174 and 217. These results provide a platform for further structural investigations of the HSulf enzymes, aiming at deciphering the role of each chain in the substrate binding and specificities and in the catalytic activities.     

SUMF2对炎症的影响

炎症是机体的一种适应性反应,失调时将会对自身机体造成损伤。研究表明许多疾病的发生发展均与炎症的失调有关。硫酸酯酶作为人体不可或缺的蛋白质家族与炎症之间有着密切关联。发热是炎症最主要的表现形式,硫酸酯酶修饰因子2(sulfatase-modifying factor 2,SUMF2)参与硫酸酯酶的激活且与发热密切相关。脂多糖刺激人体后,SUMF2的表达明显降低。SUMF2已被证实与白细胞介素-13(Interleukin-13,IL-13)之间存在相互作用,且能在体外水平抑制IL-13的分泌,IL-13可以通过抑制炎性因子的产生发挥抗炎作用。本文将就硫酸酯酶、SUMF2及其对炎症之间的影响进行综述。     

硫酸酯酶2型基因体内表达促进化疗药物诱发的小鼠骨髓抑制恢复作用研究

采用半定量RT-PCR和重组基因体内表达法观察了硫酸酯酶2基因（Sulfatase 2,Sulf2）在5-氟脲嘧啶（5-Fluorouracil, 5-Fu）诱发的小鼠骨髓抑制和再生过程中作用。结果表明：Sulf2在小鼠骨髓抑制和再生过程中呈现先上升,后下降的动态表达;电转pcDNA3.1-Sulf2基因实验组外周血白细胞数和血小板数在5-Fu注射后第7天分别为(1216.7±457.9)/μl和(8.1±5.4)万/μl,明显低于对照组［分别为(1691.7±228.9)/μl和(14.7±2.1)万/μl］,实验组单条腿骨髓细胞总数在第7天为(94.2±21.1)万,显著低于对照组（173±59.9）万,但在第11天为(585±337.9)万,又显著地高于对照组（255±65.3）万,实验组第7天10000个骨髓细胞总集落形成数为(9±8.4),显著低于对照组（39±12.2),统计均有显著性差异（p<0.05）。这些结果提示Sulf2可能对5 Fu诱发的小鼠骨髓抑制后的再生具有促进作用。     

Molecular Characterization of Arylsulfatase G: EXPRESSION,PROCESSING, GLYCOSYLATION,TRANSPORT, AND ACTIVITY*

Arylsulfatase G (ARSG) is a recently identified lysosomal sulfatase that was shown to be responsible for the degradation of 3-O-sulfated N-sulfoglucosamine residues of heparan sulfate glycosaminoglycans. Deficiency of ARSG leads to a new type of mucopolysaccharidosis, as described in a mouse model. Here, we provide a detailed molecular characterization of the endogenous murine enzyme. ARSG is expressed and proteolytically processed in a tissue-specific manner. The 63-kDa single-chain precursor protein localizes to pre-lysosomal compartments and tightly associates with organelle membranes, most likely the endoplasmic reticulum. In contrast, proteolytically processed ARSG fragments of 34-, 18-, and 10-kDa were found in lysosomal fractions and lost their membrane association. The processing sites and a disulfide bridge between the 18- and 10-kDa chains could be roughly mapped. Proteases participating in the processing were identified as cathepsins B and L. Proteolytic processing is dispensable for hydrolytic sulfatase activity in vitro. Lysosomal transport of ARSG in the liver is independent of mannose 6-phosphate, sortilin, and Limp2. However, mutation of glycosylation site N-497 abrogates transport of ARSG to lysosomes in human fibrosarcoma cells, due to impaired mannose 6-phosphate modification.     

Gender differences in the levels of bisphenol A metabolites in urine

The metabolism of bisphenol A (BPA), a suspected endocrine disruptor, should be considered for monitoring human exposure to BPA, because the conjugation with beta-D-glucuronide and sulfate reduces the estrogenic activity. In this study, BPA levels in 30 healthy Koreans (men, N=15, 42.6+/-2.4 years; women, N=15, 43.0+/-2.7 years) were analyzed from urine treated with/without beta-glucuronidase and/or sulfatase by an RP-HPLC with fluorescence detection. The total BPA concentrations including free BPA and the urinary conjugates were similar in men and women (2.82+/-0.73 and 2.76+/-0.54 ng ml(-1), respectively), but gender differences were found in the levels of urinary BPA conjugates. Men had significantly higher levels of BPA-glucuronide (2.34+/-0.85 ng ml(-1)) than women (1.00+/-0.34 ng ml(-1)), whereas women had higher levels of BPA-sulfate (1.20+/-0.32 ng ml(-1)) than men (0.49+/-0.27 ng ml(-1)).     

A sensitive HPLC method for the assessment of metabolic conversion of estrogens

Disorders of estrogen-responsive tissues are frequently associated with aberrations in steroid metabolism due to altered expression of synthesizing and metabolizing enzymes. For instance, overexposure to unopposed 17β-estradiol has been associated with the pathogenesis of endometrial proliferative disorders, such as endometriosis. Investigations into the metabolic conversion in tissues and cells have been rather limited. This is mostly due to fact that such studies have to make use of radioactive steroid hormones and expensive equipment to obtain sufficient sensitivity.

We adapted a sensitive non-radioactive HPLC method to study estrogen metabolism in more detail. This HPLC method is based on the solid phase extraction of estrogens and the derivatization of the steroids with 2-(4-carboxy-phenyl)-5,6-dimethylbenzimidazole. The technique is sensitive, robust and is useful for the detection of aromatase, 17β-HSD types 1 and 2 and sulfatase activities in lysates of placenta and endometrium.