Genetic control of glucuronidase in mice

Beta-glucuronidase activity in prostatic carcinoma and benign prostatic hyperplasia

Beta-glucuronidase activity was extracted from prostatic carcinomas and hyperplastic prostates. It was 3.6-fold higher (P less than 0.0001) in prostatic carcinoma than in prostatic hyperplasia. Analysis for isoenzymes of prostatic beta-glucuronidase by disc-gel electrophoresis in nondenaturing polyacrylamide gels demonstrated only one form of the enzyme. Histochemically, enzymatic activity was observed almost entirely in epithelial cells in both prostatic carcinoma and benign prostatic hyperplasia.

Identity of esterase-22 and egasyn, the protein which complexes with microsomal beta-glucuronidase

Recent experiments have demonstrated that egasyn not only sequesters beta-glucuronidase in microsomes by forming high molecular weight complexes with beta-glucuronidase, but also has carboxyl esterase activity. We have found several new phenotypes of egasyn-esterase after electrophoresis and isoelectric focusing of liver homogenates and purified egasyn of inbred and wild mouse strains. Several phenotypes corresponded in relative mobility and relative isoelectric point among inbred strains to that recently reported for esterase-22 by Eisenhardt and von Deimling [(1982). Comp. Biochem. Physiol. 73B:719]. This genetic evidence, plus a wide variety of comparative biochemical and physiological data, indicates that egasyn is identical to esterase-22. Both parental types of egasyn isozymes are expressed in heterozygous F1 progeny, suggesting that alterations in the egasyn structural gene are responsible for the altered isoelectric points. Also, egasyn is a monomer since no new esterase bands appear in F1 progeny. The variants in isoelectric point of egasyn map at or near the egasyn (Eg) gene within the esterases of cluster 1 near Es-9 on chromosome 8.

A survey on the formation and localization of secondary isozymes in mammalia

A survey on the formation of secondary isozymes (= multiple molecular forms of enzymes) is given by means of well-documented enzyme systems. Further examples of a certain type of formation are summarized in tabular form. Eight different classes of enzyme variants deriving from translational processes are discussed. These are: aggregation, polymerization, oxidation and reduction of free SH groups, limited proteolysis, cleavage of carbohydrate residues, deamidation, noncovalent binding of coenzymes, and conformational isomerism. In addition, the intracellular distribution of secondary isozymes is discussed, as are the formation of artificial enzyme variants and the recognition of multiple enzyme forms caused by an exchange of neutral amino acids. About 200 original papers are cited. The reference list was completed in early 1979.

Histochemical studies on genetical control of hormonal enzyme inducibility in the mouse. III. Beta-glucuronidase distribution pattern of epididymis in different genotypes

This article reports the application of Hayashi's histochemical technique for beta-glucuronidase to mouse epididymis. A methodological study, which established optimal conditions for demonstrating the enzyme in this organ, is reported. The distribution pattern of beta-glucuronidase is described and correlated with previous data for alpha-naphthyl acetate esterase. Differences between sites of granular and diffuse reaction product for these two enzymes are recorded. Possible interpretations of these findings in terms of intracellular localization of enzymes are discussed. Studies on different strains reveal regular differences in histochemical organization between mice of various genotypes. Histochemical data which imply androgen inducibility of beta-glucuronidase in mouse epididymis are preliminary noted.

Relationships between levels of membrane-bound glucuronidase and the associated protein egasyn in mouse tissues

Mouse beta-glucuronidase has a dual intracellular localization, being present in both endoplasmic reticulum and lysosomes of several tissues. Previous studies demonstrated that the protein egasyn is complexed with microsomal but not lysosomal glucuronidase and that a mutant lacking egasyn is deficient in microsomal, but not lysosomal, glucuronidase. By means of a recently developed radioimmunoassay for egasyn, the relationship between microsomal glucuronidase levels and egasyn levels has been examined in various adult tissues, during postnatal development in liver, and after androgen induction of glucuronidase in kidney. The results indicate that the relative availability of egasyn determines the balance between glucuronidase incorporation into membranes and that into lysosomes.

The molecular genetics of mammalian glucuronidase

The genetic factors known to be involved in the final realization of beta-glucuronidase activity in mice are considered from the standpoint of structural genes determining the catalytic activity of enzyme molecules as well as the recognition features of enzyme molecules that identify them for subsequent processing by the cell; processing genes determining the cellular apparatus involved with the conjugation, intracellular localization and eventual degradation of enzyme molecules; regulatory genes determining rates of enzyme synthesis, especially in response to physiological signals such as hormones; and temporal genes determining the developmental programs for expression of these classes during growth and differentiation. The properties of genetic variants of beta-glucuronidase falling into each of these classes are described. When those results are considered in concert with the properties of genetic variants known for other mammalian enzymes several generalizations emerge. Structural genes of enzymes are not usually linked to the processing genes determining the post-assembly events in the life of that enzyme. In contrast, all of the regulatory and temporal gene sites so far identified are in close proximity to the structural genes they modulate. Regulatory and temporal sites appear to act in a cis fashion to control the amount of enzyme synthesized from the adjacent structural allele on the same chromosome.

Rabbit beta-glucuronidase. Purification and properties, and the existence of multiple forms

1. beta-Glucuronidase (EC 3.2.1.31) was purified from rabbit liver by a procedure involving autolysis, (NH(4))(2)SO(4) fractionation, chromatography on DEAE-cellulose and hydroxyapatite, gel filtration, sedimentation in a sucrose gradient, and isoelectric focusing. 2. Electron microscopy revealed ferritin as the major contaminant in later stages of purification and also showed aggregates of enzyme molecules. Particular attention was paid to the removal of ferritin. 3. The purified enzyme was homogeneous in polyacrylamide-gel electrophoresis both in non-dissociating conditions and in the presence of sodium dodecyl sulphate, and in Ouchterlony gel diffusion and immunoelectrophoresis against polyspecific antisera. 4. Sedimentation in sucrose gradients gave a molecular weight of 300000, whereas gel filtration indicated 440000. 5. Subunits of 75000 molecular weight were observed in gel electrophoresis in the presence of sodium dodecyl sulphate and in gel filtration in the presence of urea. 6. The K(m) value for p-nitrophenyl beta-d-glucuronide was 0.6mm, and the enzyme was extremely sensitive to lactone inhibitors. It was also inhibited by Hg(2+) ions. 7. Multiple forms were observed in the pure enzyme by isoelectric focusing, with pI values of 4.5-5.8. Subunits showed similar heterogeneity. The origin of the multiple forms was investigated in detail, and the possibility of artifact generation largely excluded. Some of the forms of lowest pI disappeared after neuraminidase digestion. The nature of the residual heterogeneity remains to be elucidated.

Physicochemical modifications of lysosomal hydrolases during intracellular transport

1. The following fractions were prepared from rat kidney and characterized ultrastructurally, biochemically and enzymically: (a) an ordinary rough microsomal (RM(1)) fraction; (b) a special rough microsomal (RM(2)) fraction enriched seven- to nine-fold in acid hydrolases over the homogenate; (c) a smooth microsomal (SM) fraction; (d) a Golgi (GM) fraction enriched 2.5-fold in acid hydrolases and 10-, 15- and 20-fold in sialyltransferase, N-acetyl-lactosamine synthetase and galactosyltransferase respectively; (e) a lysosomal (L) fraction enriched 15- to 23-fold in acid hydrolases. The frequency of Golgi sacs and tubules seen in the electron microscope and the specific activity of the three glycosyltransferases in these fractions increased in the order: RM(2)<RM(1)<SM<GM. 2. Five lysosomal hydrolases, acid phosphatase, beta-N-acetyl-hexosaminidase, beta-galactosidase, beta-glucuronidase and arylsulphatase, were characterized in these fractions with respect to (a) solubility on freeze-thawing and (b) electrophoretic mobility in polyacrylamide gels. 3. In the RM(2) fraction each of these hydrolases occurred largely or exclusively as a single bound basic form coincident with cationic glycoprotein bands in gels (Goldstone et al., 1973). 4. In the L fraction these hydrolases were present largely as soluble, acidic (anionic) forms. 5. The solubility, electrophoretic heterogeneity and anodic mobility of these hydrolases increased progressively in subcellular fractions in the order: RM(2)<RM(1)<SM<GM<L. 6. These findings, together with evidence cited in the text showing that N-acetylneuraminic acid residues are responsible for the solubility and electronegative charge of these acidic forms and incorporation of these residues into the Golgi apparatus, support the following scheme for the biosynthesis of lysosomal enzymes. Each hydrolase is synthesized as a bound basic glycoprotein enzyme in a restricted portion of the rough endoplasmic reticulum. The soluble, acidic forms are generated as the nascent glycoprotein enzymes migrate through the Golgi apparatus through the attachment of sugar sequences containing N-acetylneuraminic acid.