[Combined cytoreductive surgery and intraoperative hyperthermic chemo-perfusion for peritoneal carcinomatosis: methods, postoperative features and end results]

Peritoneal carcinomatosis is detected in 10-40% of patients with "first look" peritoneal tumors. Median survival after chemotherapy is generally 2-6 months. Use of cytoreductive surgery and intraoperative intraperitoneal chemohyperthermic perfusion (ISHTP) improves the end results significantly. The study included 45 cases of surgery: gastric cancer (15), ovarian and cervical carcinoma ('17), colorectal cancer (8) and miscellaneous cancers involving advanced peritoneal carcinomatosis (5). ISHTP procedure was carried out immediately after cytoreductive surgery including peritonectomy (Sugarbaker). Postoperative complication and lethality frequency was 37.7 and 22.2%, respectively; mean survival--17 months. Eight patients have survived without signs of relapse; three of them--for more than 2 years. Cytoreductive surgery plus ISHTP protocol for peritoneal carcinomatosis increases survival time 3-fold and improves quality of life.

Molecular mechanism of lysosomal sialidase deficiency in galactosialidosis involves its rapid degradation

Galactosialidosis is an inherited lysosomal storage disease caused by the combined deficiency of lysosomal sialidase and beta-galactosidase secondary to the deficiency of cathepsin A/protective protein, which is associated with sialidase and beta-galactosidase in a high-molecular weight (1.27MDa) complex. Clinical phenotypes of patients as well as the composition of compounds which are stored in patient's tissues implicate sialidase deficiency as the underlying pathogenic defect. The recent cloning and sequencing of lysosomal sialidase [Pshezhetsky, Richard, Michaud, Igdoura, Wang, Elsliger, Qu, Leclerc, Gravel, Dallaire and Potier (1997), Nature Genet. 15, 316-320] allowed us to study the molecular mechanism of sialidase deficiency in galactosialidosis. By Western blotting, using antibodies against the recombinant human enzyme, and by NH2-terminal sequencing, we showed that sialidase is synthesized as a 45.5 kDa precursor and after the cleavage of the 47-amino acid signal peptide and glycosylation becomes a 48.3 kDa mature active enzyme present in the 1.27 kDa complex. Transgenic expression of sialidase in cultured skin fibroblasts from normal controls and from galactosialidosis patients, followed by immunofluorescent and immunoelectron microscopy showed that in both normal and affected cells the expressed sialidase was localized on lysosomal and plasma membranes, but the amount of sialidase found in galactosialidosis cells was approximately 5-fold reduced. Metabolic labelling studies demonstrated that the 48.3 kDa mature active form of sialidase was stable in normal fibroblasts (half-life approximately 2.7 h), whereas in galactosialidosis fibroblasts the enzyme was rapidly converted (half-life approximately 30 min) into 38.7 and 24 kDa catalytically inactive forms. Altogether our data provide evidence that the molecular mechanism of sialidase deficiency in galactosialidosis is associated with abnormal proteolytic cleavage and fast degradation.

Comparative modeling of substrate binding in the S1' subsite of serine carboxypeptidases from yeast, wheat, and human

Human cathepsin A ("lysosomal protective protein"; E.C.3.4.16.5) is a multifunctional lysosomal protein which forms a high-molecular-weight complex with beta-galactosidase and alpha-neuraminidase, protecting them against intralysosomal proteolysis. In addition to this protective function, cathepsin A is a serine carboxypeptidase and the understanding of its catalytic function requires a definition of its substrate specificity. For this purpose, we used a combined experimental [Pshezhetsky, A. V., Vinogradova, M. V., Elsliger, M.-A., El-Zein, F., Svedas, V.K., & Potier, M. (1995) Anal. Biochem. 230, 303-307] and theoretical approach comparing cathepsin A to two different homologous carboxypeptidases of the same family: yeast carboxypeptidase Y and wheat carboxypeptidase II. We computed the energies involved in substrate binding to the S1' subsite (C-terminal) of cathepsin A using a structural model based on the X-ray structure of the homologous wheat carboxypeptidase II. The binding energies of N-blocked Phe-Xaa dipeptide substrates to the active sites of cathepsin A, wheat carboxypeptidase II, and yeast carboxypeptidase Y were estimated using a molecular mechanics force field supplemented with a solvation energy term. This theoretical analysis showed a good correlation with the experimentally determined free energies of substrate binding. This result validates the use of this approach to analyze the energetics of substrate binding to the S1' subsite and provides a rational interpretation of serine carboxypeptidase-substrate interactions in molecular terms. We conclude that the three serine carboxypeptidases have similar affinities for substrates with hydrophobic P1' amino acid residues but that the wheat enzyme has an additional capacity for binding positively charged P1' residues. Finally, the substrate specificity of human cathepsin A is very similar to that of carboxypeptidase Y, with a high binding affinity for substrates with hydrophobic P1' residues, but the affinity of cathepsin A for P1; Phe residue is higher than for the Leu residue.

Continuous spectrophotometric assay of human lysosomal cathepsin A/protective protein in normal and galactosialidosis cells

We describe a method to determine the substrate specificity of human lysosomal carboxypeptidase, cathepsin A/protective protein, using furylacryloyl (FA)-Phe-X dipeptides as substrates. These dipeptides contain a chromophore which allows continuous spectrophotometric assay at wavelengths above 324 nm with little interference from protein absorbance. The results obtained with cathepsin A purified from human placenta demonstrate that the enzyme has the highest affinity for substrates with large hydrophobic (Phe, Leu) or positively charged (Arg) amino acid residues in P1' position. The three substrates (FA-Phe-Phe, FA-Phe-Leu, and FA-Phe-Ala) which demonstrated the highest specificity (kcat/Km) for the purified enzyme were then used to assay cathepsin A activity in cultured skin fibroblasts from patients affected with galactosialidosis, an inherited lysosomal storage disease caused by the genetic deficiency of cathepsin A. Residual cathepsin A activity in galactosialidosis fibroblasts was lower than 6% of controls, indicating the high specificity of the assay method.

Human lysosomal beta-galactosidase-cathepsin A complex: definition of the beta-galactosidase-binding interface on cathepsin A

Human lysosomal beta-galactosidase is organized as a 680-kDa complex with cathepsin A (also named carboxypeptidase L and protective protein), which is necessary to protect beta-galactosidase from intralysosomal proteolysis. To understand the molecular mechanism of beta-galactosidase protection by cathepsin A, we defined the structural organization of their complex including the beta-galactosidase-binding interface on cathepsin A. Radiation inactivation analysis suggested the existence of a 168-kDa structural subunit of the complex containing both beta-galactosidase and cathepsin A. Chemical cross-linking of the complex confirmed the existence of this subunit and showed that it is composed of one cathepsin A dimer and one beta-galactosidase monomer. The modeling of the cathepsin A dimer tertiary structure based on atomic coordinates of a wheat carboxypeptidase suggested a putative beta-galactosidase-binding cavity formed by the association of two cathepsin A monomers. According to this model two exposed loops of cathepsin A bordering the cavity were chosen as part of a putative beta-galactosidase-binding interface. Synthetic peptides corresponding to these loops were found both to dissociate the complex and to inhibit its in vitro reconstitution from purified cathepsin A and beta-galactosidase. The defined location of the GAL monomer in the complex with 35% of its surface covered by the CathA dimer may explain the stabilizing effect of CathA on GAL in lysosome.

[The effect of glycolipids [correction of glycoproteins] on the oligomeric structure and catalytic activity of alpha-L-fucosidase from human kidneys]

alpha-L-Fucosidase (EC 3.2.1.51) has been isolated from human kidney and purified to homogeneity by affinity chromatography on concanavalin A-Sepharose and fucosylamino-Sepharose. The catalytic activity and oligomeric structure of the enzyme were studied in a reversed micelle system of aerosol OT in octane. Depending on the degree of hydration (a parameter determining the geometrical sizes of the inner aqueous cavity of micelles), fucosidase is present within micelles as 53 kDa monomers, 110 kDa dimers, 230 kDa tetramers and 480 kDa octamers. Association of the monomers into tetra- or octamers causes a 3-4 fold increase in the specific catalytic activity of alpha-L-fucosidase. At pH and ionic strength values corresponding to intralysosomal ones alpha-L-fucosidase is isolated from tissues exclusively in a tetrameric form. After treatment with sodium cholate and subsequent dialysis this tetramer irreversibly dissociates into monomers; this reaction is accompanied by 2-3-fold decreases in the specific catalytic activity of alpha-L-fucosidase. The enzyme tetrameric structure and specific catalytic activity may be reconstituted in a reversed micelle system in the presence of glycolipids-di- and trihexosylceramides, GM1-ganglioside and a mixture of bovine brain gangliosides.

[Human glycosidase in the AOT reversed micelle system: features of properties and kinetic regularities of catalysis]

Kinetic of hydrolysis, by lysosomal glycosidases, of their synthetic substrates were studied in systems of the Aerosol OT (AOT) reversed micelles in octane. Catalytic activity of all the tested enzymes, viz., GM1-galactosidase, beta-hexosaminidases A and B, neuraminidase, and galactocerebrosidase, in reversed micelles proved to be the same as or higher than in the water buffer. In the reversed micelles an effective inhibition of the enzymatic reactions by the resulting carbohydrates was however observed. The dependence of the enzymes' activity on the hydration degree was represented by curves with one or several maxima, corresponding to various oligomeric forms of the enzymes. Dependencies of effective Km on the hydration degree in reversed micelles are similar dependencies of the enzyme activities on the same parameter, which can be explained by corresponding changes of local substrate concentration near the enzyme active site. Dependencies of the enzymatic activity on the surfactant's concentration in the reversed micellar system were also studied. Catalytic activity of the soluble lysosomal glycosidases was found to be unaffected by the micelles concentration. Activity of the membrane lysosomal glycosidase, galactocerebrosidase, strongly increased when the surfactant's concentration decreased. Under optimal conditions the activity of galactocerebrosidase in reversed micelles was 10-fold as compared with its activity in the water buffer.

[Interaction of EcoRII restriction and modification enzymes with synthetic DNA fragments. Determination of the size of EcoRII binding site]

EcoRII restriction endonuclease binding site has been determined on the basis of comparison of the binding parameters of the enzyme with synthetic DNA-duplexes of concatemer type containing a different number of EcoRII recognition sites. It has been shown that it consists of 21 +/- 1 base pairs.