USE OF YEAST BETA-GALACTOSIDASE IN MILK AND MILK PRODUCTS1

1971 ◽  
Vol 34 (6) ◽  
pp. 294-299 ◽  
Author(s):  
W. L. Wendorff ◽  
C. H. Amundson ◽  
N. F. Olson ◽  
J. C. Garver
Keyword(s):  
Maximum Rate ◽  
Inhibitory Effect ◽  
Potassium Sulfate ◽  
Factors Affecting ◽  
Milk Products ◽  
Dry Milk ◽  
Rate Of Hydrolysis ◽  
Milk Solids ◽  
Hydrolysis Of ◽  
Beta Galactosidase

Experiments were carried out to study factors affecting the enzyme activity of β-galactosidase of Saccharomyces fragilis NRRL Y-1109 in milk products. Both the type of lactose-containing substrates and their method of preparation greatly affected β-galactosidase activity. Lactose in an aqueous solution was hydrolyzed more easily than it was in milk products. Of milk products tested, whey was the best substrate for the enzyme. Milk solids, other than lactose, exhibited some inhibitory effect on hydrolysis of lactose by the S. fragilis β-galactosidase. The maximum rate of hydrolysis in milk products was obtained when milk or whey was fortified with 0.1 M potassium sulfate and 10−4 M manganese chloride. Nonfat dry milk and whey powders, in which portions of the lactose were hydrolyzed to simple sugars, were prepared. These products were of good flavor, appearance, and stability.

scholarly journals Evidence for the regulation of guinea-pig heart microsomal phosphatidylcholine-hydrolysing phospholipase A1 by guanosine 5′-[γ-thio]triphosphate

1992 ◽  
Vol 288 (3) ◽  
pp. 965-968 ◽  
Author(s):  
K Badiani ◽  
X Lu ◽  
G Arthur
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Guinea Pig ◽  
Molecular Species ◽  
Inhibitory Effect ◽  
Phospholipase A1 ◽  
Guinea Pig Heart ◽  
Substrate Specificities ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

We have recently characterized lysophospholipase A2 activities in guinea-pig heart microsomes and postulated that these enzymes act sequentially with phospholipases A1 to release fatty acids selectively from phosphatidylcholine (PC) and phosphatidylethanolamine, thus providing an alternative route to the phospholipase A2 mode of release. In a further investigation of the postulated pathway, we have characterized the PC-hydrolysing phospholipase A1 in guinea-pig heart microsomes. Our results show that the enzyme may have a preference for substrates with C16:0 over C18:0 at the sn-1 position. In addition, although the enzyme cleaves the sn-1 fatty acid, the rate of hydrolysis of PC substrates with C16:0 at the sn-1 position was influenced by the nature of the fatty acid at the sn-2 position. The order of decreasing preference was C18:2 > C20:4 = C18:1 > C16:0. The hydrolyses of the molecular species were differentially affected by heating at 60 degrees C. An investigation into the effect of nucleotides on the activity of the enzyme showed that guanosine 5′-[gamma-thio]triphosphate (GTP[S]) inhibited the hydrolysis of PC by phospholipase A1 activity, whereas GTP, guanosine 5′-[beta-thio]diphosphate (GDP[S]), GDP, ATP and adenosine 5′-[gamma-thio]triphosphate (ATP[S]) did not affect the activity. The inhibitory effect of GTP[S] on phospholipase A1 activity was blocked by preincubation with GDP[S]. A differential effect of GTP[S] on the hydrolysis of different molecular species was also observed. Taken together, the results of this study suggest the presence of more than one phospholipase A1 in the microsomes with different substrate specificities, which act sequentially with lysophospholipase A2 to release linoleic or arachidonic acid selectively from PC under resting conditions. Upon stimulation and activation of the G-protein, the release of fatty acids would be inhibited.

Methylsteroids. VII. Factors Affecting the Hydrolysis of 7α- and 11β-Acetoxylanostanes

1961 ◽  
Vol 14 (1) ◽  
pp. 48
Author(s):  
CS Barnes ◽  
BD Beilby
Keyword(s):  
Carbonyl Group ◽  
Carbonyl Groups ◽  
Factors Affecting ◽  
Steric Crowding ◽  
Methylene Groups ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Methylene Group

Doubly bonded methylene groups have been introduced into 7α- and 11β-acetoxylanostanes and the rate of hydrolysis compared with compounds having a hydroxy or carbonyl group at the same position as the methylene group. It was found that methylene groups facilitate hydrolysis of the hindered acetoxy groups in the same way, but not to the same extent, as carbonyl groups. It is concluded that the facilitation in each case results from a conformational disturbance, but that there is some other factor involved in carbonyl facilitation. It was not possible to demonstrate a similar effect resulting from steric crowding of substituents.

LACTOSE HYDROLYSIS IN MILK AND MILK PRODUCTS BY BOUND FUNGAL BETA-GALACTOSIDASE

1973 ◽  
Vol 36 (1) ◽  
pp. 31-33 ◽  
Author(s):  
J. H. Woychik ◽  
M. V. Wondolowski
Keyword(s):  
Aspergillus Niger ◽  
Skim Milk ◽  
Lactose Hydrolysis ◽  
Batch Reactors ◽  
Galactosidase Activity ◽  
Milk Products ◽  
Sweet Whey ◽  
Acid Whey ◽  
Hydrolysis Of ◽  
Beta Galactosidase

The β-galactosidase of Aspergillus niger was immobilized by glutaraldehyde coupling to porous glass beads and the bound enzyme evaluated for its applicability to hydrolysis of lactose in milk and milk products. Lactose in sweet whey and skim milk was hydrolyzed at approximately one-third the rate in acid whey. Non-lactose solids inhibited β-galactosidase activity. Greater efficiency of lactose hydrolysis was obtained with the bound enzyme in column operations than in stirred batch reactors.

Improved Microbiological Procedure for Determining Erythromycin in Milk and Some Milk Products

1980 ◽  
Vol 63 (5) ◽  
pp. 1144-1148
Author(s):  
Carol P Harpster ◽  
Stanley E Katz
Keyword(s):  
Microbiological Assay ◽  
Maximum Sensitivity ◽  
Cream Cheese ◽  
Milk Products ◽  
Dry Milk ◽  
Agar Layer ◽  
Nonfat Dry Milk ◽  
Milk Solids ◽  
Supernatant Solution

Abstract An improved microbiological assay for erythromycin in milk and some milk products was developed. Acidification of the samples to pH 4.5 resulted in precipitation of milk solids which were separated by centrifugation. The pH of the aqueous supernatant solution was readjusted to pH 8.0 to obtain maximum sensitivity. The sample cleanup and the use of a single, thin, seeded agar layer with Micrococcus lutea as the assay organism permitted the measurement of 0.05 μg/mL milk with recoveries averaging 84.0%, 0.50 μg/g nonfat dry milk with recoveries averaging 55.4%, 0.10 μg/g cream cheese with recoveries averaging 100.2%, and 0.05 μg/mL buttermilk with recoveries averaging 44.0%. The improved procedures showed superior recoveries and improved the ability to detect and measure lower levels when compared with commonly recommended assay procedures for erythromycin residues.

Solvolysis of Sulphonyl Halides. IV. The Hydrolysis of Some Substituted Aliphatic Sulphonyl Chlorides and of Ethanesulphonyl Bromide in Aqueous Dioxan

1962 ◽  
Vol 15 (4) ◽  
pp. 684 ◽  
Author(s):  
R Foon ◽  
AN Hambly
Keyword(s):  
Maximum Rate ◽  
Pure Water ◽  
Aqueous Media ◽  
Sulphur Atom ◽  
Enthalpy Of Activation ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Chlorine Bond ◽  
Transition Complexes ◽  
Continuous Range

The effects of substitution in the alkyl group of an alkanesulphonyl chloride, on the rate of hydrolysis, vary with the solvent composition. The relative rates can be explained in terms of the theory of Grunwald and Winstein that there is a continuous range of transition complexes, with " bond making " between the water molecule and the sulphur atom controlling the rate in the less aqueous media, while the stretching and charging of the sulphur to chlorine bond controls the rate in solvents of higher water content. The inhibition of the simple SN2 reaction, which gives rise to a maximum rate constant as the composition of the solvent approaches pure water, resembles that noted with methane- and ethanesulphonyl chlorides.�The hydrolysis of ethanesulphonyl bromide, at 25 �C, proceeds at three to eight times the rate for the corresponding sulphonyl chloride in solvents varying in composition from 0.99 to 0.2 mole fraction of water with dioxan. Over most of the solvent range both the entropy and enthalpy of activation are favourable to a higher rate of solvolysis for the sulphonyl bromide.

Factors affecting the rate of hydrolysis of starch in legumes

1985 ◽  
Vol 42 (1) ◽  
pp. 38-43 ◽  
Author(s):  
S Wong ◽  
K Traianedes ◽  
K O'Dea
Keyword(s):  
Factors Affecting ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

INACTIVATION OF LUTEINIZING HORMONE RELEASING HORMONE BY RAT HYPOTHALAMIC L-CYSTINE ARYLAMIDASE

1975 ◽  
Vol 78 (4) ◽  
pp. 634-648 ◽  
Author(s):  
Herbert Kuhl ◽  
Hans-Dieter Taubert
Keyword(s):  
Inhibitory Effect ◽  
Supernatant Fraction ◽  
Luteinizing Hormone Releasing Hormone ◽  
Lysine Vasopressin ◽  
Hormone Effects ◽  
Rate Of Hydrolysis ◽  
Lh Rh ◽  
Hydrolysis Of ◽  
The Brain ◽  
Cystine Arylamidase

ABSTRACT The rate of hydrolysis of several aminoacyl-4-nitroanilides by rat hypothalamic arylamidases was investigated. The activity of these enzymes which were mainly found in the 105 000 × g supernatant fraction of homogenates of the hypothalamus and other parts of the brain was shown to depend upon the presence of metal ions and free thiol groups, and to be inhibited by puromycin. As previous investigations had shown that Cys-NA is an appropriate substrate for measuring hormone effects on hypothalamic arylamidases, L-cystine arylamidase and its interaction with various peptide hormones were examined in detail. It could conclusively be shown that this enzyme interacts particularly with oligopeptides. Its activity was competitively inhibited by TRF, oxytocin, lysine vasopressin, and LH-RH. It was also shown that the biological activity of LH-RH and its inhibitory effect on the hydrolysis of L-cystine-bis-p-nitroanilide decreased when it was incubated for various periods of time with the 105 000 × g supernatant of rat hypothalamus homogenate.

FACTORS AFFECTING UREASE ACTIVITY IN A BLACK SPRUCE HUMUS STERILIZED BY GAMMA RADIATION

1968 ◽  
Vol 48 (3) ◽  
pp. 355-361 ◽  
Author(s):  
M. R. Roberge ◽  
R. Knowles
Keyword(s):  
Picea Mariana ◽  
Maximum Rate ◽  
Urease Activity ◽  
Radiation Flux ◽  
Ph Value ◽  
Black Spruce ◽  
Factors Affecting ◽  
Measured Activity ◽  
Rate Of Hydrolysis ◽  
Sterilization Dose

Factors affecting the activity of urease were studied in a black spruce (Picea mariana (Mill.) B S P.) humus sampled at Baie-Comeau, Quebec, and sterilized with a Co-60 source. The enzyme was almost completely inactivated by 4–5,000 kr (about four times the sterilization dose). For a given dose, the measured activity was somewhat lower when a lower radiation flux was used with a longer exposure time. A substrate concentration of 50–100 mg/g urea-N was required for maximum rate of hydrolysis. Even at a much lower concentration (3.5 mg/g), hydrolysis was linear during the first 12 hr of reaction at 20 °C. Urease activity was approximately proportional to temperature in the range 10–40 °C. Activity showed a slight decrease as water content was increased from 60 to 140% of maximum holding capacity. In humus buffered at different pH's, the activity was at a maximum at about pH 7.0. In the absence of buffer, however, activity was higher than when buffered at either the initial or the final pH value of the unbuffered system. Activity did not change as buffer concentration in the samples was increased from 0.25 to 1.00 M.

scholarly journals The β-glucosidase from Botryodiplodia theobromae Pat. Kinetics of enzyme-catalysed hydrolysis of o-nitrophenyl β-d-glucopyranoside in dioxan/water

1978 ◽  
Vol 175 (2) ◽  
pp. 455-459 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Maximum Rate ◽  
Buffer System ◽  
Botryodiplodia Theobromae ◽  
Hydrolytic Reaction ◽  
Anomeric Carbon ◽  
Rate Of Hydrolysis ◽  
Beta Glucosidase ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Anomeric Carbon Atom

1. The hydrolysis of o-nitrophenyl beta-D-glucopyranoside by the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) from Botryodiplodia theobromae Pat. has been studied in the presence of added dioxan. 2. At donor saturation, the maximum rate of hydrolysis in the presence of up to 50%(v/v) dioxan was pH4.3-4.5 (pH of the buffer system in water) in McIlvaine's buffer. 3. Increasing dioxan concentrations progressively decreased the maximum rate of hydrolysis. 4. The rate of enzyme-catalysed reaction was enhanced at high donor concentrations, but inhibited at low donor concentrations in the presence of glycerol, methanol, fructose of sucrose. 5. The hydrolytic reaction was found to proceed with retention of configuration at the anomeric carbon atom. 6. The kinetics of the enzyme-catalysed process in the presence of added acceptors indicated that water was necessary for the maintenance of the active enzyme conformation apart from its acceptor function.

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