Isoenzyme patterns of human liver alpha-L-fucosidase during development

Change of isoforms' spectra of alpha-L-fucosidase from human skin fibroblasts in intracellular storage of nonhydrolyzable substances

The effect of exogenous and endogenous products storage in lysosomes on the activity and multiple forms of alpha-L-fucosidase from human skin fibroblasts was investigated. It was shown that sucrose load, modelling intralysosomal accumulation of nonhydrolyzable products, causes certain changes in secretion level of alpha-L-fucosidase and multiple forms' spectra of the intracellular and secreted enzymes. These changes were different for the enzyme from embryonal and postnatal normal fibroblasts. Some changes of secreted alpha-L-fucosidase isoforms' spectra were found in fibroblasts from a patient with Fabry's disease, characterized by the intralysosomal storage of di- and trihexosylceramides. The alterations of isoforms' profiles in Fabry fibroblasts at the early and late accumulation stages were similar to those in sucrose-loaded embryonal and postnatal fibroblasts, respectively. It is proposed that intralysosomal accumulation of nonhydrolyzable compounds influences the alpha-L-fucosidase posttranslational processing.

Analysis of purified human liver alpha-L-fucosidase by western-blotting with lectins and polyclonal and monoclonal antibodies

Western-blot analysis [with lectins, polyclonal antibodies (pAbs) and four monoclonal antibodies (mAbs)] was employed to investigate the structural relationship between the separated isoforms and subunits of purified human liver alpha-L-fucosidase. SDS/PAGE and Western-blot analysis indicated the presence of two protein bands of 51 kDa and 56 kDa that were recognized by the pAbs. Polyacrylamide-gel isoelectric focusing (PAG-IEF) followed by blotting indicated that the pAbs and mAbs recognized at least five fucosidase isoforms (pI values 3.6-6.0). Lectin blotting indicated an enrichment of sialic acid residues in the more acidic isoforms. Western-blot analysis indicated that four mAbs recognized the 51 kDa subunit and at least two mAbs recognized the 56 kDa subunit. The subunit composition of the isoforms (separated by PAG-IEF) of human liver alpha-L-fucosidase was investigated by SDS/PAGE. One or two closely spaced bands were found for each isoform with a trend of increasing relative amounts of the high-molecular-mass band in the more acidic isoforms relative to the more neutral isoforms. Neuraminidase treatment of alpha-L-fucosidase resulted in a decrease in the amount of the high-molecular-mass subunit and an increase in the amount of the low-molecular-mass subunit, suggesting that these subunits are related at least in part by sialic acid residues. In addition, blotting with lectins indicated the presence of sialic acid residues only in the high-molecular-mass subunit. N-Glycanase treatment led to the disappearance of the glycosylated 56 kDa and 51 kDa protein bands and the appearance of non-glycosylated protein bands at 48 kDa and 45 kDa. The overall results indicate that (1) N-glycosylation contributes to, but does not account completely for, structural differences in the fucosidase subunits and (2) the more acidic isoforms of fucosidase contain enriched relative amounts of the sialylated high-molecular-mass subunit.

Mammalian alpha-L-fucosidases

Mammalian alpha-L-fucosidases are a ubiquitous group of relatively large multimeric lysosomal glycosidases involved in the degradation of a diverse group of naturally-occurring fucoglycoconjugates. These enzymes are closely related structurally as indicated by immunochemical cross-reactivity and cloning studies. Mammalian fucosidases are sialoglycoproteins and the carbohydrate, particularly sialic acid, contributes to producing multiple isoforms which can differ in various species as well as in different tissues within a given species. alpha-L-Fucosidases exhibit maximal activity at pH values between 4 and 7, have similar kinetic properties with synthetic substrates (PNP-fucoside and 4-MU-fucoside), and exhibit broad substrate specificity on natural substrates. Numerous linkages (alpha 1-2, alpha 1-3, alpha 1-4, alpha 1-6), primarily to galactose and N-acetylglucosamine, can be hydrolyzed but preference is often seen for small mol. wt water-soluble substrates with fucose in alpha 1-2 linkage to galactose. The importance of alpha-L-fucosidase in mammalian metabolism is evidenced by deficiency or absence of its enzymatic activity leading to a fatal genetic disease, at least in humans and English Springer Spaniels.

Isoform, kinetic and immunochemical characterization of rodent liver alpha-L-fucosidases

alpha-L-Fucosidase from hamster and six inbred mouse strains contains two to three unique basic isoelectric forms (above pI 7.0) in addition to the usual acidic and neutral isoforms from pI 4-7. Rat liver alpha-L-fucosidase contains multiple isoforms between pI values of 4.0 and 7.3 whereas guinea pig liver alpha-L-fucosidase exhibits a single broad isoform at pI 5.3. 2. All the alpha-L-fucosidases have similar KM values (0.05-0.12 mM) for 4-methylumbelliferyl-alpha-L-fucopyranoside but pH-activity curves which are significantly different in optima and per cent of optimal activity in the acid region. 3. Double-antibody immunoprecipitation experiments indicate that rodent liver alpha-L-fucosidases crossreact to varying extents with polyclonal antibody against human liver alpha-L-fucosidase. 4. Hamster, guinea pig and mouse liver alpha-L-fucosidases exhibit significantly less binding than human and rat liver fucosidases to the agarose-epsilon-aminocaproylfucosamine affinity resin.

Alpha-L-fucosidase activity in normal human lymphocytes

After DEAE-Trisacryl chromatography two forms of alpha-L-fucosidase have been characterized in normal human lymphocytes. These enzymatic forms were different with respect to their optimum pH, kinetic properties and isoelectric behaviour. After neuraminidase treatment two forms are still observed with a neutral shift in pI values. These results suggest that at least two structurally different alpha-L-fucosidase units exist.

Biochemical aspects of alpha-L-fucosidase in hepatocellular carcinoma

Biochemical characteristics of alpha-L-fucosidase (alpha-L-fucoside hydrolase, EC 3.2.1.51) were studied in tumorous and nontumorous human hepatocellular carcinoma (n = 14). Five parameters were studied: (i) specific activity, (ii) thermostability, (iii) enzyme affinity for an artificial substrate (Km), (iv) isoenzyme patterns of the glycosidase before and after neuraminidase treatment and (v) pH influence on enzyme activity. The specific activity of alpha-L-fucosidase was significantly decreased in tumoral liver when compared to nontumoral liver. The curve of pH activity constantly showed a broad optimum centered near pH 5, whereas two optima were always observed in nontumoral areas. In contrast, there was no modification of the thermostability, the substrate affinity and the isoenzyme patterns of alpha-L-fucosidase in hepatocellular carcinoma.

Purification and kinetic studies of an alpha-L-fucosidase of Venus mercenaria

An alpha-L-fucosidase activity has been isolated from the liver (hepatopancreas) of the common edible clam, Venus mercenaria, and has been purified approximately 300-fold (11% yield) by affinity chromatography on agarose-epsilon-amino-caproylfucosamine. Isoelectric focusing profiles were heterogeneous, revealing several isoenzymes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated the presence of a single subunit of Mr 50,000. The purified enzyme preparation contained only trace amounts of other alpha- and beta-D-glycosidases tested. In addition to p-nitrophenyl alpha-L-fucopyranoside, the enzyme hydrolyzed natural substrates such as fucose-containing milk pentasaccharides, thyroglobulin glycopeptides, human salivary glycoproteins, and blood-group-active glycosphingolipids. The enzyme preparation had a broad pH optimum range between 4.5 and 5.5. The apparent Km value with respect to p-nitrophenyl alpha-L-fucopyranoside was 0.26mM.

Variation in alpha-L-fucosidase properties among 28 inbred mouse strains: six strains have high enzyme activity and heat-stabile enzyme with a variant pH-activity curve; twenty-two strains have low activity and heat-labile enzyme

Alpha-L-fucosidase in tissues of 28 inbred mouse strains varied with respect to three properties: high or low heat stability, a pH-activity curve with high or low relative activity at pH 2.8, and high or low activity. Alpha-L-fucosidase from six strains (A/J, BDP/J, LP/J, P/J, SEA/GNJ, and 129/J) had high heat stability, high pH 2.8 relative activity, and high activity, whereas the other 22 strains all had low heat stability, low pH 2.8 relative activity, and low activity. The heat-stability difference was seen in all organs tested (brain, liver, kidney, spleen, heart, skeletal muscle, lung, and testis) for two heat-stabile strains (P/J and 129/J) and four heat-labile strains (C57BL/6J, C3H/HeJ, DBA/2J, and BALB/cJ) studied in detail. The findings suggested that two structural variants of alpha-L-fucosidase, probably genetically determined, exist in these 28 inbred mouse strains, although the presence of linkage disequilibrium between alleles of tightly linked structural and regulatory genes could not be excluded.

Demonstration of human alpha-L-fucosidase polymorphism by means of monoclonal antibodies

Conventional rabbit antibodies and mouse monoclonal antibodies were raised to alpha-L-fucosidase purified from human placenta. Four monoclonal antibodies were studied, of which only one (A) was able to immunoprecipitate the fucosidase activity completely. Two antibodies (B and C) precipitated 65% and one (D) 35% of the activity. The enzyme precipitated by the monoclonal antibodies remained fully active, whereas the enzyme precipitated by conventional antibodies was partly inactivated. As shown by the method of successive immunoprecipitations, the monoclonal antibodies B and C recognized the same set of placental fucosidase molecules, and D a subset thereof. The purified fucosidase also yielded two components after gel electrophoresis in nondenaturing conditions, and the slower component corresponded to the set recognized by antibodies B and C. The fucosidase extracted from different tissues and serum was studied by immunoprecipitation. In all cases, the enzyme was completely precipitated by monoclonal antibody A. Two patterns were found with B, C and D: either part of the activity was precipitated by these antibodies (leucocytes, placenta, brain, liver, spleen, thymus) or B, C and D failed to precipitate any of the enzyme (serum, heart, kidney, testes).

Isoelectric forms of alpha-L-fucosidase in mouse teratocarcinoma-derived cell lines

The alpha-L-fucosidase isoenzyme pattern of mouse teratocarcinoma-derived cell lines was analyzed by isoelectric focusing and compared with the pattern of a mammary carcinoma as an example of a malignant somatic cell line. In addition, these isoenzyme patterns were compared with those of normal fetal and adult mouse tissues from an earlier study. In the normal early fetal and placental tissues as well as in embryonal carcinoma and yolk sac carcinoma cells the alpha-L-fucosidase activity is predominantly associated with basic forms of the enzyme. This embryonic pattern of alpha-L-fucosidase is characterized by one to three isoelectric forms of the enzyme with pI values ranging from 7 to 9.5 accounting for more than two-thirds of the total activity. In contrast, the mammary carcinoma pattern resembles adult somatic tissues and primarily expresses acidic enzymatic forms (which comprise approximately 80% of total activity). The somatic cell malignancies arising in retransplantable teratocarcinomas show varying isoenzyme patterns. Thus, a malignant fibrous histiocytoma expresses predominantly basic forms of the enzyme, whereas a leiomyosarcoma expresses approximately equal amounts of acidic and basic forms of the enzyme resembling in this respect late fetal or immature neonatal tissues. These findings show that the embryonal carcinoma and yolk sac carcinoma cells of the mouse express the embryonic isoenzyme pattern of alpha-L-fucosidase in contrast to malignant cells originating in somatic tissue, like mammary carcinoma, which express the adult pattern. Malignancies arising in somatic tissues of teratocarcinomas may retain the embryonic alpha-L-fucosidase phenotype or show a phenotype corresponding to late fetal or neonatal tissues in normal ontogeny.

Characterization of mouse liver alpha-L-fucosidase. Demonstration of unusual basic isoelectric forms of the enzyme that appear to be developmentally regulated

Mouse tissues contain unusual basic isoelectric forms of alpha-L-fucosidase (with approximate isoelectric points of 8.3 and 9.0) in addition to the usual acidic and neutral forms previously described in tissues of other species. These unusual forms are very prominent in placenta and foetal tissues and comprise approx, 50-80% of total activity up to 11 days of postnatal development. By 15 days of postnatal development, the basic forms are diminished in amount and comprise not more than 25% of total activity. Neuraminidase treatment of adult mouse liver alpha-L-fucosidase led to significantly decreased amounts of acidic forms and increased amounts of the basic forms, suggesting that these forms are chemically related at least in part by sialic acid residues. Comparative kinetic studies on mouse liver, human liver and mouse placental alpha-L-fucosidases indicated that they have the same Km (0.05-0.06 mM) for 4-methylumbelliferyl alpha-L-fucopyranoside but different pH optima and thermostability properties. Mouse liver alpha-L-fucosidase has one pH optimum (5.5) and an acidic shoulder (centred around pH 4.0) compared with two distinct optima (4.3 and 6.8) for the human liver enzyme. Mouse placental alpha-L-fucosidase has a pH-activity curve comparable with that of the mouse liver enzyme except that the acidic shoulder is absent. Mouse liver alpha-L-fucosidase is considerably more thermolabile after preincubation at 50 degrees C than are the human liver and mouse placental enzymes, which gave similar thermodenaturation curves. Immunochemical studies indicated that mouse and human alpha-L-fucosidases are dissimilar antigenically but exhibit some cross-reactivity. The IgG fraction of antibody prepared in goat against human liver alpha-L-fucosidase was ineffective by itself in immunoprecipitating mouse liver alpha-L-fucosidase, but 63% and 72% of the mouse liver and placental enzymes respectively could be immunoprecipitated in the double-antibody experiments under conditions that immunoprecipitated 92% of the human liver enzyme.

Radioimmunochemical evidence for a role of carbohydrate in antigenic determinant(s) on human liver alpha-L-fucosidase

A competitive-binding radioimmunoassay method was employed to investigate the role of carbohydrate in antigenic determinant(s) of human liver alpha-L-fucosidase. Competition curves were used to quantify the concentrations of competitors needed to cause 30% inhibition of the precipitation of 125I-labelled alpha-L-fucosidase. The isoelectric forms of alpha-L-fucosidase, which are related by sialic acid residues, were separated preparatively and used as competitors in the radioimmunoassay. A pattern of increasing effectiveness as competitors with increasing acidity of the forms was found, suggesting that sialic acid may be involved in the antigenic determinant(s) of alpha-L-fucosidase. Specificity was exhibited when sugar and sugar derivatives were used as competitors in the radioimmunoassay: a 51-fold range of competitive ability was found, and sialic acids (N-acetylneuraminic acid and N-glycollylneuraminic acid) and colominic acid (a polymer of N-acetylneuraminic acid) were the best competitors. The results of our studies suggest that carbohydrate contributes to antigenic determinant(s) of alpha-L-fucosidase and that sialic acid is probably the major sugar involved.

Presence of an atypical thermolabile species of beta-hexosaminidase B in metastatic-tumour tissue of human liver

An atypical thermolabile species of Hex B (hexosaminidase B) has been found in metastatic-tumour sites of human liver which has a thermostability curve similar to that of Hex A (hexosaminidase A), which is present in decreased amounts relative to the Hex A isoenzyme, and which exhibits decreased relative activity at acidic pH values (2.6-3.6) when compared with control-liver Hex B. This atypical Hex B isoenzyme has a normal apparent Michaelis constant (0.6 mM) for 4-methylumbelliferyl 2-deoxy-2-acetamido-beta-D-glucopyranoside. The presence of this atypical Hex B suggests that variant beta-chains are being produced in metastatic-tumour tissue.

Activity levels and properties of acid alpha-glucosidase from liver and neutral alpha-glucosidase from sera of cystic fibrosis patients and controls

The average activity levels of acid alpha-glucosidase are comparable in liver supernatant fluids for 15 cystic fibrosis patients and 12 controls (401 +/- 131 and 347 +/- 109 nmol/h/mg protein, respectively) and no significant differences were found for the cystic fibrosis and control liver acid alpha-glucosidases in their (a) apparent Km values for the 4-methylumbelliferyl substrate (1.1 mmol/l), (b) pH optima (4.2) and thermostability curves and (c) isoelectric profiles (one form with an isoelectric point of 4.5 +/- 0.2). In contrast, average neutral alpha-glucosidase activity levels were significantly increased (p less than 0.0002) in sera from 21 cystic fibrosis patients compared to 15 controls (10.7 and 2.7 nmol/h/ml). This increased activity is not due to (a) different stability upon storage at --20 degrees C, (b) the presence of activators in cystic fibrosis sera or inhibitors in normal sera (as determined by mixing studies), (c) altered Km values or (d) altered pH optima curves. Cystic fibrosis serum neutral alpha-glucosidase appears to be more thermostable and has a consistently altered isoelectric profile (greater percentage of activity above pI 4.8) when compared to the normal serum enzyme. This altered isoelectric composition may reflect changes in neutral alpha-glucosidase which contribute to its increased activity in cystic fibrosis sera.

alpha-L-Fucosidase in cystic fibrosis: analysis of skin fibroblasts and liver

The lysosomal enzyme alpha-L-fucosidase has been examined by thin layer gel and column isoelectric focusing in skin fibroblasts and liver from patients with cystic fibrosis and controls. All three common phenotypes of the enzyme were observed in both control and CF fibroblasts. When individuals of the same alpha-L-fucosidase phenotype were compared, no major differences between the isozyme profiles of cystic fibrosis patients and controls were detected in either fibroblasts or liver tissue.

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.

Thermostability of human alpha-L-fucosidase. Relationship to fucosidosis and low-activity serum alpha-L-fucosidase

Thermostability studies have been performed at different preincubation temperatures (37-65 degrees C) on human alpha-L-fucosidase (alpha-L-fucoside fucohydrolase, EC 3.2.1.51), purified serum and liver enzyme, the isoelectric forms of purified liver enzyme which were separated by preparative isoelectric focusing, crude adult and fetal liver supernatant enzyme and neuraminidase-treated enzyme. Very different thermostability curves were found for the various isoelectric forms of alpha-L-fucosidase. The most neutral form (I) is least thermostable and the most acidic form (VIII) most thermostable, with the intervening forms (II-VII) having intermediate thermostabilities. For the isoelectric forms of liver alpha-L-fucosidase there appars to be a significant trend of increasing thermostability with increasing acidity (and presumably, increasing amounts of sialic acid). In order to determine what role, if any, sialic acid plays in determining the thermostability of alpha-L-fucosidase, comparative thermostability studies were performed on alpha-L-fucosidases from different human tissues which are reported to contain varying amounts of sialic acid. The purified sialic acid-rich serum enzyme is considerably more thermostable than the purified liver enzyme. The fetal liver enzyme (which is less acidic and may contain less sialic acid than the adult liver enzyme) is less thermostable than adult liver alpha-L-fucosidase. In contrast to all of the above findings which suggest that sialic acid confers thermostability to alpha-L-fucosidase, neuraminidase treatment of human liver alpha-L-fucosidase did not change its thermostability, even when considerable desialylation occurred as monitored by isoelectric focusing. The reason for these apparently inconsistent findings is not clear at the present time but several possible interpretations of the data are given.

Human amniotic fluid alpha-L-fucosidase

The activity and properties of alpha-L-fucosidase in 24 samples of amniotic fluid have been investigated using the 4-methylumbelliferyl substrate. A wide range of fucosidase specific activity (0.20-1.45 nmol/min/mg protein) was found with an average value of 0.62 nmol/min/mg protein. Although no clear-cut correlation exist, there appear to be trends of decreasing fucosidase specific activity with increasing maternal age of donor and increasing gestational time. alpha-L-Fucosidase activity from four amniotic fluids was characterized kinetically and immunochemically and found not to differ in its properties due to maternal age of donor or gestational time. Isoelectric focusing revealed multiple forms between pH 5.0 and 6.8, with the majority of activity present between pH 5.0 and 6.0. The pH optimum is near pH 5.0 with a second optimum suggested at pH 6.2. The apparent Michaelis constant (Km) for the 4-methylumbelliferyl substrate is 0.05 +/- 0.01 mM. The enzyme is completely thermostable at 37 degrees C for at least 4 h but loses 95% of its activity after preincubation at 45 degrees C for 1 h. Double immunodiffusion and immunoprecipitation experiments using anti-liver alpha-L-fucosidase antibody suggest that the amniotic fluid alpha-L-fucosidase is antigenically similar, if not identical, to the human liver enzyme.

Multiple forms of epidermal alpha-fucosidase

Two forms of alpha-fucosidase from newborn rat epidermis were separated by gel filtration on Sephadex G-150. These enzymes termed, fucosidase I which was eluted in the void volume and fucosidase II (molecular weight approximately 50,000). Both enzymes had pH optima for 4-methylumbelliferyl-alpha-L-fucoside hydrolysis between 5.5-6.5. Km values for fucosidase I and II with the same substrate were 3.7 X 10(-5) and 5.4 X 10(-5) M, respectively. Three different forms of new born rat epidermal alpha-fucosidase were separated by isoelectric focusing. Evidence is present which indicates that the electrophoretic heterogeneity of alpha-fucosidase is due in part to the binding of sialic acid to the primary gene product.

Purification and characterization of altered cystic fibrosis liver alpha-L-fucosidase

alpha-L-Fucosidase (E.C.3.2.4.51) from two cystic fibrosis livers has been purified and characterized. Purification was accomplished by an affinity chromatographic procedure previously used for normal liver alpha-L-fucosidase. Characterization of the two cystic fibrosis alpha-L-fucosidases indicated that they were very similar to normal liver alpha-L-fucosidase with regard to pH optima profiles, Michaelis constants (Km's), subunit structure and antigenicity. However, gas liquid chromatographic analysis revealed altered carbohydrate compositions for both the cystic fibrosis alpha-L-fucosidases. The three major sugars found in normal purified liver alpha-L-fucosidase (mannose, N-acetylglucosamine and sialic acid) were reduced in the cystic fibrosis alpha-L-fucosidases, on average, to 51%, 44% and 32%, respectively, of their normal amounts.

Cystic fibrosis liver sialyltransferase

The activity of sialytransferase with regard to the glycoprotein substrates asialofetuin and asialo-ovine submaxillary mucin was determined in normal, pathological control, and cystic fibrosis liver homogenates. Cystic fibrosis and pathological livers have about 40% of the average normal specific activity for sialytransferase. Several properties of cystic fibrosis sialytransferase were investigated and compared to those of the normal liver enzyme (Alhadeff et al. 1977). The pH optima curves were similar, but cystic fibrosis sialyltransferase appears to be more thermolabile than the normal liver enzyme. Isoelectric focusing studies revealed that the three most basic forms of sialyltransferase which are found in normal livers are deficient or absent in most cystic fibrosis liver. The data suggest that altered glycoprotein-sialyltransferases may be present in cystic fibrosis livers, probably a secondary effect due to general liver pathology.

Human serum alpha-L-fucosidase

Human serum alpha-L-fucosidase has been purified 241 200-fold with 35% yield by an affinity chromatographic procedure utilizing agarose-epsilon-aminocaproyl-fucosamine. Isoelectric focusing of the purified enzyme indicated the presence of several forms, with the form at pI 5.0 comprising the majority of the activity. Assay of the purified alpha-L-fucosidase showed only trace amounts of contaminating glycosidases present, with beta-galactosidase being the largest contamnant (0.5% by activity). Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated the presence of two subunits with very similar molecular weights (56 500 and 54 000). Using the p-nitrophenyl substrate, the purified serum alpha-L-fucosidase has an apparent Michaelis constant of 0.52 mM and a broad pH optimum centered around pH 4.8 with a second, minor optimum at pH 6.1. Gel filtration on Sepharose 6-B indicated an apparent molecular weight of 296 000 +/- 30 000. Preincubation with antibodies made previously against purified liver alpha-L-fucosidase led to quantitative immunoprecipitation of the purified serum alpha-L-fucosidase. Assay of the purified serum alpha-L-fucosidase for sialic acid indicated the presence of 1.7 microgram sialic acid per 100 microgram enzyme, about twice that previously found for the purified liver enzyme.

Carbohydrate composition of purified human liver alpha-L-fucosidase

Human liver alpha-L-fucosidase was purified to apparent homogeneity and analyzed for carbohydrate content primarily by gas-liquid chromatography (glc). The enzyme is about 7% carbohydrate by weight and contains the following sugars (residues per 50, 000 molecular weight subunit): mannose (8.3), glucosamine (4.3) (presumably N-acetylated), sialic acid (1.6) and glucose (1.6). Galactose (0.8) and L-fucose (1.8) were also found but their presence may be due to artifacts of the purification procedure.

Glycosphingolipid hydrolases: properties and molecular genetics

This is a review of the properties and molecular genetics of six lysosomal hydrolases: beta-galactosidase, hexosaminidases A and B, alpha-galactosidase, beta-glucosidase and alpha-fucosidase. Each enzyme is discussed with regards to isoenzymes and substrate specificity, subunit structure, genetic relationship of isoenzymes and genetic variants. The molecular genetics of human diseases caused by deficiencies of each enzyme are discussed.

Prenatal diagnosis of fucosidosis

A pregnancy from a family at risk for fucosidosis was monitored. Determinations of fucosidase and mannosidase were performed on the serum and white blood cells of several members of the family, om amniotic fluid and amniotic fluid cells of the fetus at several passages, and on fibroblast cell lines from index cases. The fetus was diagnosed as being free from the disease. This conclusion was confirmed after birth by fucosidase determination in plasma and white cells from cord blood, and in the placenta. Fluctuations in fucosidase activity were observed in extracts from cultured amniotic cells at various passages. The possible causes of this variability are discussed.

Altered isoenzyme patterns of liver alpha-L-fucosidase in cystic fibrosis

The isoenzyme pattern of alpha-L-fucosidase was studied by isoelectric focusing in livers from seven patients with cystic fibrosis and in normal and pathological (GM1-gangliosidosis, Type II and Sanfilippo disease) controls. The controls had very reproducible patterns consisting of seven isoenzymes of alpha-L-fucosidase with the most neutral from (I) representing a small proportion of the total activity. All seven of the cystic fibrosis livers had altered alpha-L-fucosidase isoenzyme patterns. The chemical relationship of the seven isoenzymes of normal liver alpha-L-fucosidase was investigated using neuramindase. The five most acidic forms of alpha-L-fucosidase appear to be related to the most neutral form by sialic acid residues. Since the isoenzymes of liver alpha-L-fucosidase appear to be related by sialic acid residues, it is possible that the altered alpha-L-fucosidase isoenzyme patterns found in cystic fibrosis livers may result from aberrant sialylation.