scholarly journals Human small-intestinal β-galactosidases. Separation and characterization of one lactase and one hetero β-galactosidase

1969 ◽  
Vol 114 (2) ◽  
pp. 351-359 ◽  
Author(s):  
Nils-Georg Asp ◽  
Arne Dahlqvist ◽  
Otakar Koldovský
Keyword(s):  
Intestinal Mucosa ◽  
Gel Filtration ◽  
Competitive Inhibitor ◽  
The Other ◽  
Artificial Substrates ◽  
Small Intestinal Mucosa ◽  
Lactase Activity ◽  
Ph Optimum ◽  
Small Intestinal

1. Two β-galactosidases from human small-intestinal mucosa were separated by gel-filtration chromatography and the properties of the two enzymes were studied. Lactose and four hetero β-galactosides were used as substrates. 2. One of the enzymes was particle-bound and could be partially solubilized with papain. Of the substrates hydrolysed by this enzyme, lactose was hydrolysed most rapidly. This enzyme is thus essentially a disaccharidase and is named lactase. It is presumably identical with the ‘lactase 1’ described earlier. 3. The other enzyme was mainly soluble and hydrolysed all artificial substrates used, whereas no lactase activity could be detected. This enzyme has therefore been designated hetero β-galactosidase. 4. p-Chloromercuribenzoate (0·1mm) inhibited the hetero β-galactosidase completely but did not influence the activity of the lactase. Tris was a competitive inhibitor of both enzymes. 5. The residual lactase activity in the mucosa of lactose-intolerant patients may be exerted by a small amount of remaining lactase as such, or possibly by a third enzyme with a more acid pH optimum.

scholarly journals Human small-intestinal β-galactosidases. Separation and characterization of three forms of an acid β-galactosidase

1971 ◽  
Vol 121 (2) ◽  
pp. 299-308 ◽  
Author(s):  
Nils-Georg Asp
Keyword(s):  
Intestinal Mucosa ◽  
Total Activity ◽  
Small Intestinal Mucosa ◽  
Lactase Activity ◽  
Considerable Part ◽  
Ph Optimum ◽  
Rate Of Hydrolysis ◽  
Small Intestinal ◽  
Hydrolysis Of

1. An acid β-galactosidase, optimum pH4.0–4.5, in the human small-intestinal mucosa was separated and characterized. 2. Autolysis of mucosal homogenates at acid pH inactivated the lactase and hetero β-galactosidase; the total activity of the acid β-galactosidase was only slightly depleted, but a greater proportion of the enzyme was solubilized by this treatment. 3. Separation on a Sephadex G-200 column revealed that the acid β-galactosidase could occur in at least three different forms, probably representing monomer, dimer and octamer or polymer of the enzyme. 4. The properties of the different forms of the acid β-galactosidase were studied with regard to pH optimum, Km, rate of hydrolysis of different substrates, and sensitivity to p-chloromercuribenzoate and tris as inhibitors. All these properties were the same for the different forms of the enzyme. 5. The acid β-galactosidase hydrolyses lactose as well as hetero β-galactosides and contributes to the lactase activity of intestinal biopsies also when measured at pH 6. This enzyme may therefore be responsible for a considerable part of the residual lactase activity found in lactose-intolerant patients.

scholarly journals Rat small-intestinal β-galactosidases. Kinetic studies with three separated fractions

1968 ◽  
Vol 110 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Nils-Georg Asp ◽  
Arne Dahlqvist
Keyword(s):  
Active Sites ◽  
Kinetic Studies ◽  
Competitive Inhibitor ◽  
Small Intestinal Mucosa ◽  
Lactase Activity ◽  
Freezing And Thawing ◽  
Ph Optimum ◽  
Measurable Rate ◽  
Small Intestinal ◽  
Hydrolysis Of

1. Three fractions of β-galactosidase activity from the rat small-intestinal mucosa were separated chromatographically. Two of these fractions had an acid pH optimum at 3–4, and the third one had a more neutral pH optimum at 5·7. 2. The two ‘acid’ β-galactosidase fractions had considerably lower Km values for hetero β-galactosides than for lactose. The Vmax. values were similar for all the substrates used (lactose, phenyl β-galactoside, o-nitrophenyl β-galactoside, p-nitrophenyl β-galactoside and 6-bromo-2-naphthyl β-galactoside). No difference could be detected between the two ‘acid’ fractions with respect to their enzymic properties (pH optimum, Km for the different substrates, Ki for lactose as an inhibitor of the hydrolysis of hetero β-galactosides, Ki for phenyl β-galactoside as an inhibitor of the hydrolysis of lactose, and relative Vmax. for the hydrolysis of different substrates). These two fractions probably represent different forms of the same enzyme. 3. The ‘neutral’ fraction had similar Km values for all the substrates hydrolysed, but with lactose as substrate the Vmax. was much higher than with the hetero β-galactosides. This fraction did not split phenyl β-galactoside or 6-bromo-2-naphthyl β-galactoside at a measurable rate. 4. Lactose was a competitive inhibitor of the hetero β-galactosidase activities of all the three fractions, and Ki for lactose as an inhibitor in each case was the same as Km for the lactase activity. Phenyl β-galactoside was a competitive inhibitor of the lactase activity of all the three fractions. These facts strongly indicate that in all the three fractions lactose is hydrolysed by the same active sites as the hetero β-galactosides. 5. Human serum albumin stabilized the separated enzymes against inactivation by freezing and thawing.

Purification and preliminary characterization of 2-monoacylglycerol acyltransferase from rat intestinal villus cells

1985 ◽  
Vol 63 (5) ◽  
pp. 341-347 ◽  
Author(s):  
F. Manganaro ◽  
A. Kuksis
Keyword(s):  
Specific Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Cell Protein ◽  
Racemic Mixture ◽  
Small Intestinal Mucosa ◽  
Small Intestinal ◽  
Monoacylglycerol Acyltransferase

We have purified the monoacylglycerol acyltransferase from rat small intestinal mucosa to homogeneity by a combination of hydrophobic absorption, guanidine dissociation, and gel filtration. The purified enzyme gives a single band of 37 000 daltons on sodium dodecyl sulphate – polyacrylamide gel electrophoresis. The enzyme has a specific activity of about 5900 nmol/mg per hour and represents 0.12% of total cell protein, corresponding to about a 600-fold purification. The enzyme does not acylate diacylglycerols to triacylglycerols, which is consistent with the separate physical existence of the mono- and di-acylglycerol acyltransferases. The enzyme acylates the 2-monoacylglycerols to yield an essentially racemic mixture of diacylglycerols. It does not acylate glycerol 3-phosphate.

scholarly journals Phosphodiesterase II in epithelial cells from guinea-pig and rat small intestine

1974 ◽  
Vol 142 (3) ◽  
pp. 545-553 ◽  
Author(s):  
Peter R. Flanagan ◽  
S. H. Zbarsky
Keyword(s):  
Epithelial Cells ◽  
Guinea Pig ◽  
Specific Activity ◽  
Soluble Fraction ◽  
Gel Filtration ◽  
Equilibrium Density ◽  
Small Intestinal Mucosa ◽  
Ph Optimum ◽  
Triton Wr 1339 ◽  
Small Intestinal

Phosphodiesterase II activity was determined by using a synthetic substrate, the 2,4-dinitrophenyl ester of thymidine 3′-phosphate. The enzyme activity was determined in fractions obtained by differential centrifugation of homogenates of epithelial cells from the small intestinal mucosa of guinea pigs and rats. In guinea-pig preparations phosphodiesterase II occurred with highest specific activity in those fractions rich in succinate dehydrogenase and acid phosphatase. A lysosomal location for the guinea-pig enzyme was indicated by its structure-linked latency and by its association with particles that under-went a characteristic decrease in equilibrium density when Triton WR-1339 was injected into the animals. With rat preparations a much greater proportion of the phosphodiesterase II activity was found in the soluble fraction after ultracentrifugation. The rat enzyme exhibited a lower degree of latency and administration of Triton WR-1339 had no effect. The rat enzyme further differed from that of the guinea pig in other respects; it was more labile at 60°C, it exhibited a lower pH optimum and it had a higher molecular weight as determined by gel-filtration chromatography.

Fructose-1,6-biphosphatase activity in the intestinal mucosa of developing rats

1984 ◽  
Vol 246 (6) ◽  
pp. G683-G686
Author(s):  
K. Westbury ◽  
P. Hahn
Keyword(s):  
Intestinal Mucosa ◽  
High Fat Diet ◽  
Single Injection ◽  
Distal Portion ◽  
Small Intestinal Mucosa ◽  
High Fat ◽  
Ph Optimum ◽  
Wide Range ◽  
Old Rats ◽  
Small Intestinal

Fructose-biphosphatase (EC 3.1.3.11) activity was determined in the proximal and distal parts of the small intestinal mucosa of rats 1-30 days of age. Activity was found to increase to a maximum on about the 10th postnatal day and then to decrease. It was always higher in the proximal than in the distal portion of the gut. The enzyme showed a wide range of pH optimum around 7.0 and was inhibited by AMP. In 10-day-old rats activity determined 24 or 48 h after a single injection of cortisone or triiodothyronine was significantly decreased. This effect was no longer found for cortisone in 14-day-old animals. Weaning 18-day-old rats to a high-fat diet for 5 or 7 days delayed but did not prevent the usual decrease in activity seen at weaning.

Characterization of xenobiotic metabolizing enzymes in bovine small intestinal mucosa

2009 ◽  
Vol 33 (3) ◽  
pp. 295-303 ◽  
Author(s):  
G. VIRKEL ◽  
M. CARLETTI ◽  
M. CANTIELLO ◽  
L. DELLA DONNA ◽  
G. GARDINI ◽  
...  
Keyword(s):  
Intestinal Mucosa ◽  
Small Intestinal Mucosa ◽  
Metabolizing Enzymes ◽  
Xenobiotic Metabolizing Enzymes ◽  
Small Intestinal
Sign in / Sign up

Export Citation Format

Share Document