Biochimica et Biophysica Acta (BBA) - Specialized Section on Enzymological Subjects最新文献

Maltase (maltose glycohydrolase), isomaltase (isomaltose glycohydrolase), sucrase (sucrose glucohydrolase), palatinase (palatinose glucohydrolase), trehalase (trehalose glucohydrolase), lactae (lactose galactohydrolase) and cellobiae (cellobiose glucohydrolase) activities have been determined in the intestine of adult and suckling rats. All disaccharidase activities have been found to have the same distribution through the different sections of small intestine except for trehalose glucohydrolase activity which decreased distally more than the other disaccharides.

At birth lactose galactohydrolase and cellobiose glucohydrolase are very active, maltose glucohydrolase is low, and the other α-disaccharidases are absent. These activities appear on the 15th to 16th day after birth; at about the same time lactose galactohydrolase and cellobiose glucohydrolase activities are found to decrease.

• 1.

  1. The yield of urate oxidase (urate:O₂ oxidoreductase, EC 1.7.3.3) extracted from ox-kidney acetone powder by 0.2 M Tris (pH 10.5), was raised 1.5- to 10-fold by addition of a number of thiols, at optimum concentrations of about 8 mM.

• 2.

  2. These thiols fell into three groups, according to their action on urate oxidase extracts: (i) thioglycollic acid, BAL, mercaptoethanol, penicillamine, and ethanedithiol: (i) thioglycollic acid, BAL, mercaptoethanol, penicillamine, and etahnedithiol: no effect on urate oxidase activity; (ii) cysteine: increasing inhibition with rising concentration, up to 32 mM; (iii) GSH: increasing potentiation up to 8 mM; GSSG had no effect.

T2 DNA has been further glucosylated in vitro by the hydroxymethylcytosine α-glucosyltransferase (UDPglucose: hydroxymethylcytosine α-glucosyltransferase) specific for T4 and T6 bacteriophage in the presence of uridine disphosphate [¹⁴C] glucose. Analysis of formic acid-diphenylamine digests prepared from [¹³⁴C]DNA preparations thus synthesized has shown that it is possible to formulate differences in enzymic specificity between the various HMC α-glucosyltransferases in terms of the primary structrue of the substrat DNA. The α-transferases specific for T4 and T6 bacteriophage glucosylate HMC residues present in 5-hydroxymethyldeoxycytidine-purine doexyriboside sequences rapidly, while T2 HMC α-glucosyltransferase reacts with HMC residues at those sites at about one-twelfth of the rate.

It is also shown that the further glucosylation in excess of 28% of the free HMC residues¹ is mainly the result of an exchange reaction.

We measured (with the pH stat) the rat of hydrolysis of fibrinogen and lysine methyl ester by plasmin (EC 3.4.4.1.4) and calculated the maximal velocity (v_max) for both reactions. The v_max for the lysine methyl ester-plasmin reaction is 1.5 times greater than the v_max for the fibrinogen-plasmin reaction at pH 7.0, and at 23°. The same enzyme preparation and solvent ionic strength were used in both reactions.

A new method for measuring proteolysis of fibrinogen by plasmin is reported. This method is based on the precipitation of non-hydrolyzed fibrinogen by 9% ethanol. With this method we investigated inhibition of the fibrinogen-plasmin reaction by ω-aminocarboxylic acids and analogues of some of the 3,4,5 and 6-carbon members. Glycine, β-alanine, γ-aminobutyric acid, glutaric acid, valeric acid, cadaverine and lysine did not inhibit with concentrations less than 10 mM (K_i>10 mM). Competitive inhibition was found with δ-aminovaleric acid (K_i = 4.7 mM), ϵ-aminocaproic acid (K_i = 2.8 mM), ω-aminocaprylic acid (K_i = 1.0 mM), propylamine (K_i = 3.3 mM) < butylamine (K_i = 3.0 mM) and amylamine (K_i = 1.0 mM). Inhibition probably occurs at the active center and is probably due to both electrostatic and hydrophobic bonding of the inhibitor to the enzyme because inhibition is competitive and because inhibition is dependent on the positive charge and increases with increasing chain length of either the ω-aminocarboxylic acid or the alkylamine.

• 1.

  1. A procedure is described for the isolation of a crystalline enzyme from crude sisal extract.

• 2.

  2. The crystalline enzyme has been shown to be homogeneous by electrophoresis, chromatography on DEAE-cellulose, gel filtration on Sephadex, and solubility.

• 3.

  3. The crystalline enzyme is unstable in solution, changing spontaneously to an inactive protein of smaller molecular weight.

• 4.

  4. The identity of the crystalline enzyme with Fraction F obtained by chromatography of the crude enzyme of DEAE-cellulose has been demonstrated.

• 5.

  5. The molecular weight of the enzyme has been determined.

• 6.

  6. The trivial name agavian has been adopted for the enzyme.

• 1.

  1. Lactate dehydrogenase (l-lactate: NAD oxidoreductase, EC 1.1.1.27) isozymes from pig, beef and man have been compared by analyzing their immunological properties. The investigations were carried out mainly by means of agar precipitation techniques—immunoelectrophoretic analysis and double diffusion—in combination with a very sensitive lactate dehydrogenase (both containing mainly isozyme I and some isozyme II and III), isozyme V from pig skeletal muscle and a mixture of the five isozymes from human brain.

• 2.

  2. As we reported previously²² the isozyme I and V from pig possess different antigentic structures, as shown by a clear cut reaction of non identity in double diffusion and by absorption experiments. The failure of anti-isozyme V from pig skeletal muscle to react with isozyme I now confirms this statement.

• 3.

  In addition, a variation of immunoelectrophoretic analysis permitted us to provide evidence for the different antigenic structures of the human isozymes I and V even though we disposed only of mixtures of human isozymes.

• 4.

  The isozymes I and II from beef and from man show in immunoelectrophoretic analysis a reaction of partial identity. The isozymes I, II, and III from pig as well as II, III, and IV from man seem to be in close relation to each other.

• 5.

  All these results are in good agreement with the concept of Markert that mammalian lactate dehydrogenase molecules are composed of 4 sub-units “A” and “B”, isozyme I being the BBBB-, isozyme V the AAAA-form.

• 6.

  3. The cross reactions of lactate dehydrogenase isozymes from pig, beef, and man were studied in detail. It is shown that the cross reactions follow very closely the concept of Markert, “heart-type” cross reacting with “heart-type”, and ‘muscle-type” with “muscle-type”.

• 7.

  Absorption experiments with pure isozymes I or V and subsequent analysis of the remaining cross reactions in the respective supernatants (experiments soon to be published in detail^12,23) confirm this results.

• 8.

  The advantage of the reported cross reactions for clinical research is stressed.

An enzyme which catalyzes the cleavage of l-rhamnulose i-phosphate has been purified about 15-fold from extracts of l-rhamnose-grown Escherichia coli. The products of the reaction were characterized as dihydroxyacetone phosphate and l-lactaldehyde. The enzyme has been named l-rhanulose-phosphate aldolase. It is distinct from muscle hexose-diphosphate aldolase.