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At least 37 records · Page 2Linked to original sources
PubMed1975

Lactase-phlorizin hydrolase complex from monkey small intestine. Purification, properties and evidence for two catalytic sites.

Lactase-phlorizin hydrolase (EC 3.2.1.-) has been purified from the monkey small intestine by gel filtration and ion-exchange chromatographic procedures and the properties of the purified enzyme complex have been studied. Lactose was the most active substrate. Cellobiose and other synthetic hetero-beta-glycosides were hydrolysed at a very much reduced rate. The rate of hydrolysis of phlorizin was about 2.5% that of lactose. Lactase and phlorizin hydrolase activities were indistinguishable by heat inactivation experiments. The purified enzyme complex also hydrolysed cerebrosides. Lactose hydrolysis was competitively inhibited by phlorizin as well as by the brain cerebroside. However, there was no mutual inhibition between phlorizin and the brain cerebroside. It is suggested that the native enzyme complex might have two catalytic sites, a phlorizin site and a cerebroside site but both hydrolysing lactose.

Animals↗
PubMedDate not supplied

Intestinal lactase status of adults in Papua New Guinea.

Fifty hospital patients in Port Moresby (mean age 30 yr) without evidence of malnutrition or gastro-intestinal disease, who came from many parts of Papua New Guinea (P.N.G.), were given 50 g lactose orally after an overnight fast. In 49 blood glucose rise was less than 1.1 mmol 1(-1), indicating hypolactasia. Thirty-three gave a clear history of symptoms, usually diarrhoea, after lactose. Adult hypolactasia approaches 100% in P.N.G. There is no indication that the genetic structure of any part of the population of P,N.G. with regard to lactase has been influenced by genetic drift from peoples with persistence of lactase into adult life (PL).

Adolescent↗
PubMed1979

[Intestinal lactase and milk consumption before and after gastrectomy].

Intestinal lactase assays before and after a Billroth II procedure for chronic duodenal ulcer did not reveal a significant difference. Postoperative lactose intolerance is due to the loss of pyloric function, causing entrance of lactose into the jejunum at a rate exceeding the hydrolytic capacity of the mucosa if the lactase level is low.

Animals↗
PubMed1978

Lactase activity of microorganisms.

Sixty-two strains of yeasts, molds and bacteria were screened for lactase (beta-D-galactosidase) activity. Strains exhibiting the enzyme activity were evaluated for cell yield as well as enzyme units available per litre of the medium, per g cell dry weight and per mg protein of their cell-free extracts. The molds exhibited lowest enzyme activity but highest cell yields, bacteria produced lowest cell yield and maximum enzyme activity. Cultures exhibiting very high activity among yeasts were Saccharomyces fragilis (strain 3217) and among bacteria Streptococcus cremoris (strain H), Lactobacillus bulgaricus (strain RTS and 1373) and Leuconostoc citrovorum (strain 8081).

Bacteria↗
PubMed1977

Regulation of newly evolved enzymes. III Evolution of the ebg repressor during selection for enhanced lactase activity.

The evolution of lactose utilization by lacZ deletion strains of E. coli occurs via mutations in the ebg genes. We show that one kind of mutation in the regulatory gene ebgR results in a repressor which retains the ability to repress synthesis of ebg enzymes, but which permits 4.5-fold more ebg enzyme synthesis during lactose induction than does the wild-type repressor. A comparison between the growth rate of various ebg+ strains on lactose and the amount of ebg enzyme synthesized by these strains shows that the rate of enzyme synthesis permitted by the wild-type repressor is insufficient for growth on lactose as a sole carbon source by a cell with the most active ebg lactase yet isolated. We conclude, therefore, that the evolution of lactose utilization requires both a structural and a regulatory mutation.

Biological Evolution↗
PubMed1976

Intestinal pH and propulsion: an explanation of diarrhoea in lactase deficiency and laxation by lactulose.

Subjects deficient in lactase may experience bloating, cramps and diarrhoea after ingesting milk, due to the unhydrolysed and poorly-absorbed lactose. The diarrhoea may result from an osmotic effect of the lactose itself or its poorly-absorbed acidic products of fermentation (Weijers, van de Kamer & others, 1961; Christopher & Bayless, 1971), possibly together with an alteration of sodium and water absorption due to the lowered colonic pH (Rousseau & Sladen, 1971). Laxation by lactulose (1-4-beta-galactosidofructose) may operate through an analogous mechanism. The drug is a synthetic dissaccharide which, in oral doses of 10-20 g, relieves chronic constipation (Wesselius-de Casparis, Braadbaart & others, 1968). It is neither hydrolysed by intestinal dissaccharidase (Dahlqvist & Gryboski, 1965) nor absorbed in the gut, but it is converted in the colon mainly to lactic and acetic acids by various bacteria including Lactobacillus acidophilus. Apart from the increased osmotic effect, the pH in the proximal colon falls markedly (Bown, Gibson & others, 1974), and larger doses may reduce stool pH. Weijers & others (1961) inferred that the acidic products formed from lactose in the colon stimulate propulsion, and K.S. Liem (Philips-Duphar) suggested to us that lactulose may relieve constipation partly by stimulation of propulsion due to the lowered pH. The experiments described below support this view.

Animals↗
PubMed1978

Sucrase and lactase synthesis in suckling rat intestine in response to substrate administration.

The intestinal brush border disaccharidases separated by gel electrophoresis were studied after oral administration of a high sucrose or lactose diet to 11-day-old suckling rats during 3 days. Some modifications of the brush border protein and eyzyme patterns could be attributed to the effect of the basic diet: increase of glucoamylase, appearance of a weak sucrase activity and of a second molecular form of maltase. However, the specific action of a given disaccharide on the synthesis of the corresponding hydrolytic enzyme could be clearly demonstrated. Indeed, the electrophoretic pattern after sucrose or lactose feeding showed a marked increase of the protein bands corresponding to sucrase-isomaltase or lactase activities.

Administration, Oral↗
PubMed1977

[Influence of dietary lactose on the development of lactase activity in the digestive tract of the pig].

Lactase activity has been measured in the pancreas, the small and large intestine of 79 pigs varying in age from 6-7 months. The endogenous enzyme level fluctuated along the small intestine but the activity did not vary according to the level of lactose fed in the diet either just after weaning or from 25 to 100 kg of live weight. Measurements performed in the content of the intestine showed that lactose could be digested by the enzymes of the microflora mostly active in the ileum, the caecum and the large intestine.

Animals↗
PubMed1978

Variation in the lactase dehydrogenase activity of the esophagus.

Quantitative assay and electrophoretic study of lactate dehydrogenase (LDH) from various tissues of the opossum esophagus were performed. On the basis of expression of the LDH isozymes, we concluded that the smooth muscle of the body of the esophagus carry on more anaerobic glycolysis than the striated muscle. The smooth muscle of the gastroesophageal junction carry on both anaerobic as well aerobic glycolysis.

Animals↗