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 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 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.

scholarly journals Intestinal disaccharidase activities in the chick

1969 ◽  
Vol 112 (1) ◽  
pp. 51-59 ◽  
Author(s):  
R. C. Siddons
Keyword(s):  
Small Intestine ◽  
Large Intestine ◽  
Total Activity ◽  
Intestinal Wall ◽  
Lactase Activity ◽  
Middle Section ◽  
Ph Optimum ◽  
Ph Values ◽  
Small Intestinal ◽  
Intestinal Disaccharidases

1. Disaccharidase activities of the small and large intestines of the chick were studied. 2. Homogenates of the small intestine readily hydrolysed maltose, sucrose and palatinose (6-O-α-d-glucopyranosyl-d-fructose), hydrolysed lactose slowly and did not hydrolyse trehalose and cellobiose. 3. Within the small intestine the disaccharidases were located mainly in the intestinal wall; the activity in the contents accounted for less than 5% of the total activity. 4. The disaccharidases were non-uniformly distributed along the small intestine, the activities being greatest in the middle section. 5. The disaccharidase activities increased with age between 1 and 43 days. 6. Homogenates of the large intestine and contents readily hydrolysed maltose, sucrose, palatinose and lactose and hydrolysed cellobiose and trehalose slowly. 7. The large-intestinal disaccharidases were located mainly in the contents. 8. Similar Km and pH optimum values were found for the maltase, sucrase and palatinase activities of the large and small intestines. 9. The lactase activity of the large intestine was markedly affected by diet and had different Km and pH values from the small intestinal lactase. 10. Low activities of intestinal disaccharidase were found in 12-day-old embryos and marked increases in the intestinal disaccharidases of the developing embryo occurred 2–3 days before hatching.

Purification and characterization of an α-L-arabinofuranosidase from Clostridium acetobutylicum ATCC 824

1987 ◽  
Vol 33 (11) ◽  
pp. 1011-1016 ◽  
Author(s):  
S. F. Lee ◽  
C. W. Forsberg
Keyword(s):  
Clostridium Acetobutylicum ◽  
Culture Fluid ◽  
Purification And Characterization ◽  
Ph Optimum ◽  
Rate Of Hydrolysis ◽  
Single Polypeptide ◽  
Hydrolysis Of ◽  
Clostridium Acetobutylicum Atcc 824 ◽  
Oat Spelt

An α-L-arabinofuranosidase (EC 3.2.1.55) has been purified from the extracellular culture fluid of Clostridium acetobutylicum ATCC 824 and characterized. The enzyme was a single polypeptide with a molecular weight of 94 000, an isoelectric point of 8.15, and a pH optimum between pH 5.0 and 5.5. The Km and Vmax values for p-nitrophenyl-α-L-arabinofuranoside were 4.0 mM and 36.4 μmol∙min−1·mg protein−1, respectively. The enzyme had practically no activity against other p-nitrophenylglycosides with the exception of p-nitrophenyl-α-D-glucoside which it hydrolysed at 9% of the rate exhibited on p-nitrophenyl-α-L-arabinofuranoside. It degraded arabinan in an exo-manner, but exhibited no activity on carboxymethylcellulose, arabinogalactan, arabinoxylan, or oat spelt xylan. However, when it was incubated with the purified xylanase B, also obtained from C. acetobutylicum, it acted cooperatively to increase the rate of hydrolysis of oat spelt xylan. Arabinose was detected as one of the hydrolysis products.

DISACCHARIDASE DEFICIENCY IN INFANCY AND CHILDHOOD

PEDIATRICS ◽  
1966 ◽  
Vol 38 (1) ◽  
pp. 127-141
Author(s):  
R. R. W. Townley
Keyword(s):  
Intestinal Mucosa ◽  
Caloric Content ◽  
Lactose Hydrolysis ◽  
Small Intestinal Mucosa ◽  
Dietary Carbohydrates ◽  
New Techniques ◽  
Infancy And Childhood ◽  
The Common ◽  
Small Intestinal ◽  
Hydrolysis Of

CARBOHYDRATES provide a substantial proportion of the total caloric content of our diet. The dietary carbohydrates of quantitative importance are the polysaccharide starch and the disaccharides sucrose and lactose. Hydrolysis of each of these to monosaccharide form is necessary before significant absorption can occur. The principal product of starch digestion by amylases of the salivary glands and pancreas is maltose, a disaccharide in which two glucose units are joined by 1-4 α linkages. The other products are oligosaccharides including the disaccharide isomaltose, in which 1-6 α linkages are present. Further hydrolysis of maltose and oligo 1-6 glucosides, produced from starch, and the hydrolysis of sucrose and lactose ingested as such, is dependent on enzymes of the small intestinal mucosa, the disaccharidases. Figure 1 summarizes the sequence of digestion of the common dietary carbohydrates. For many years, clinicians have recognized that diarrhea in some patients is related to the ingestion of certain forms of carbohydrate. Recent years have seen an increasing interest in the detection of such patients, and the application of new techniques to their investigation. The development of instruments for intraluminal biopsy of the small intestinal mucosa was a notable advance, since it allowed specimens of this tissue to be obtained and some of its digestive capacities, including those concerned with disaccharide digestion, to be studied directly. By these means, it has been established that deficiency of one or more of the intestinal disaccharidases is often the basis of disaccharide intolerance. The terms "disaccharide intolerance" and "disaccharidase deficiency" are frequently used in this article, but have rather different meanings, so that a preliminary discussion of the sense in which each is used seems warranted.

Effect of fasting on Na-K-ATPase activity in rat small intestinal mucosa

1980 ◽  
Vol 58 (6) ◽  
pp. 643-649 ◽  
Author(s):  
D. Murray ◽  
G. E. Wild
Keyword(s):  
Small Intestine ◽  
Atpase Activity ◽  
Intestinal Mucosa ◽  
Total Activity ◽  
Small Intestinal Mucosa ◽  
Distal Small Intestine ◽  
Adrenocortical Activity ◽  
Glucose Ingestion ◽  
Small Intestinal ◽  
Mucosal Mass

The effect of fasting on mucosal Na-K-ATPase activity in various regions of rat small intestine was investigated. Fasting (17-48 h) was associated with a consistent decrease in specific and total activity of Na-K-ATPase in the jejunum, the levels tending to rise more distally. No effect on the specific activities of Mg-ATPase or alkaline phosphatase was found. Fasting was also associated with increased adrenocortical activity and with decreases in mucosal mass, protein content, and histological dimensions of the jejunum, no similar changes being found in the distal small intestine. Glucose ingestion prevented the decrease in jejunal enzyme activity associated with fasting and elevated levels in the mid and terminal small intestine of fed animals. These effects suggest that Na-K-ATPase activity in small intestinal mucosa may be, in part, inducible.

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