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The reaction pattern of the polygalacturonase from Helix pomatia juice has been studied. Hydrolysis of pectic acid occurs in a random manner. Oligogalacturonic acids are hydrolyzed in a sequential process, starting from the non-reducing end. This behavior is different from that of other endopolygalacturonases, which split these latter substrates both randomly and in a stepwise way from the reducing end.

When trehalose is injected via parenteral pathway into animals lacking kidney trehalase (rat), more than 75 per cent of this disaccharide is eliminated in urine. When the injected animals possess an active kidney trehalase (guinea-pig, rabbit), there is only a low urinary trehalose excretion. Moreover, in rabbit, a marked hyperglycaemia is observed which is due to the rapid hydrolysis of trehalose by kidney trehalase.

Two distinct alpha-mannosidases have been found in biological fluids by investigating the effect of pH on activity, the effect of Co2+ and Zn2+ and by determining the Michaelis constant. The two enzymes are designated as S, predominating in serum (optimum pH about 5.6) and U, predominating in urine (optimum pH about 4.2). In cerebro-spinal fluid, the amount of alpha-mannosidase S is almost the same as that of alpha-mannosidase U. Alpha-mannosidase S activity in sera is significantly higher in children than in adults.

Administration of trehalose by parenteral route to mammals (Guinea-pig and rabbit) equipped with Kidney trehalase is followed by rapid hydrolysis of the disaccharide which is excreted in urine only in very low amounts. When the animal under investigation has not trehalase in the kidney (rat), practically the total amount of trehalase is excreted in urine. Perfusion of kidney in rabbit confirms the very rapid hydrolysis of trehalose by this organ.

An alpha-L-rhamnosidase from the seeds of Fagopyrum esculentum (saracen corn) has previously been identified, and the effect of the enzyme on rhamnoisic bonds has been studied with various flavonoid glycosides. This alpha-L-rhamnosidase can be useful in structural studies, and a preliminary report of this study has appeared. The present paper describes the extensive purification of the enzyme and the determination of its properties. The purification involved extraction, ammonium sulfate fractionation and chromatography on Sephadex G 75, DEAE-Sephadex and Ultrogel AcA-44. The alpha-L-rhamnosidase was purified about 9600 fold and the final enzyme preparation was practically pure according to the criteria of disc electrophoresis. The molecular weight of this alpha-L-rhamnosidase, calculated from data obtained by disc gel electrophoresis and gel filtration, was about 70 000. Isoelectric focusing established the isoelectric point to be 3.7. The behaviour of the enzyme on a concanavalin-A-Sepharose column suggests the presence of residues resembling alpha-D-mannose or alpha-D-glucose in the protein. The various kinetic parameters, Kcat, Km and the Kcat/Km ratio have been determined at pH 5 on the following substrates: p-nitrophenyl-alpha-L-rhamnoside and rutinose (6-O-alpha-L-rhamnosyl-D-glucopyranose). All kinetics exhibit a Michaelian behaviour and the Km for the former substrate was 0.33 mM and for the latter, 2.2 mM. The Kcat/Km ratio corroborates the greater specificity of the enzyme for p-nitrophenyl-alpha-L-rhamnoside. L-Rhamnose, L-lyxose, 6-deoxy-D-glucose and methyl-alpha-D-mannoside were shown to behave strictly as competitive inhibitors of alpha-L-rhamnosidase activity; it seems that the methyl group of L-rhamnose is important for substrate binding to the enzyme.