Glucoamylase from the Predacious Fungus <Emphasis Type="Italic">Arthrobotrys conoides</Emphasis>: a Cationic Enzyme with High Debranching Activity and Raw Starch Digestibility

The extracellular amylolytic activity elaborated by the nematophagous fungus Arthrobotrys conoides was found to resolve into 2 amylolytic peaks when fractionated on Sephadex G-100 column. Around 80% of the eluted glucoamylase activity was attributed to peak I (GA A). GA A being cationic in nature was purified about 70-fold with 57% yield by negative chromatography on DEAE Sephadex at pH 7.0. The enzyme was stable over a broad pH range of 4.8–9.0. K_M for the linear polysaccharide amylose was 0.34 mg/mL. Enzyme showed high affinity for the branched polysaccharides as the K_M values for amylopectin, glycogen and starch were 0.056, 0.062 and 0.065 mg/mL, respectively. The enzyme clearly demonstrated raw starch digestibility. Probable involvement of Trp and His residues in enzyme catalysis was elucidated using group-specific reagents.     

Studies on groundnut proteins. III. Physicochemical properties of arachin prepared by different methods

The homogeneity of arachin prepared by different methods was determined by the techniques of polyacrylamide gel electrophoresis, DEAE-cellulose chromatography, and ultracentrifugation. Arachin obtained by the method of Tombs (Biochem. J.96, 119, 1965) or Dawson (Anal. Biochem.41, 305, 1971) appeared to be homogeneous by these techniques. Total groundnut proteins, extracted in 1 m NaBr solution and subjected to double precipitation with 23% (NH₄)₂SO₄, also gave a homogeneous arachin preparation. These three homogeneous arachin preparations differed in their rate of hydrolysis by alpha-chymotrypsin, heat coagulation, and dissociation into subunits. However, SDS¹ and GuHCl denatured them to the same extent, as could be judged by the difference spectra. The phosphorus and carbohydrate content of the three preparations did not differ significantly.     

A rapid method for the isolation of ribonuclease from yeast (Saccharomyces carlsbergensis).

A ribonuclease (RNAase; EC 3.1.14.1) from brewer's yeast was purified 90-fold. Crude RNAase was initially separated from other proteins by precipitation at pH 4.0 after incubation of the mechanically disrupted yeast cells at pH 6.0 and 52 degrees C for 30 min. The RNAase was purified from the supernatant by ultrafiltration with a PM-30 membrane and adsorption chromatography on hydroxyapatite. RNAase preparation was free of phosphatase, deoxyribonuclease and phosphodiesterase activities. It showed maximum activity at pH 6.0 and a temperature optimum of 52 degrees C with yeast RNA as substrate. This RNAase hydrolysed yeast RNA to nucleoside 3'-phosphates and showed no evidence of base specificity.     

Ribonuclease isolated from yeast (Saccharomyces carlsbergensis): Characterization and properties

The homogeneity of a purified ribonuclease from brewers' yeast was determined by velocity sedimentation and polyacrylamide gel electrophoresis techniques. The velocity sedimentation pattern gave a single peak with a S_app 3.46 and polyacrylamide gel electrophoresis showed one major band. The absorption spectrum of the enzyme showed maximum absorption at 277–278 nm and minimum at 252 nm. The enzyme was relatively stable to extreme pH values and high temperature. Both NaCl and KCl increased the enzyme activity whereas enzyme was inhibited by divalent metal ions. The inhibition of the enzyme was increased in the order of Ca²⁺ > Mg²⁺ > Fe²⁺Cu²⁺. Chemical modification studies of the enzyme showed that tryptophan residues and disulfide bonds were required for enzyme activity.     

Naloxone-resistant effects of opioids on the twitch in frog skeletal muscle

Morphine and several other opioid agonists including the enkephalins caused a dual action on the twitch in the isolated, curarized, and electrically stimulated frog toe muscle; a potentiating action at low drug concentrations and a potentiation followed by an inhibitory action at higher concentrations. The twitch potentiation was found to be nonstereospecific and resistant to antagonism by naloxone. The inhibitory action too was naloxone-resistant and is probably due to a nonspecific local anesthetic effect of the opioids on the electric properties of the frog skeletal muscle fibre membrane.     

Observations on bacteria associated with pigeon crop

Lactobacilli, streptococci and coliforms of pigeon crop contents, 5th wash, macerate and those of first-day pigeon milk have been studied. Streptococci predominated in all the samples tested. Relatively higher counts of lactobacilli and streptococci in crop macerate than in the 5th wash suggested the adhesion of these bacteria to crop wall. Because of frequent occurrence in crop of partially digested fibrous food, its contents were tested for the presence of cellulolytic bacteria. The results indicated that four isolates were capable of utilizing cellulose with the resultant production of reducing sugars. It is inferred that the crop microflora is involved in the degradation of dietary fibre in the pigeon.