Non-specific protein binding by adsorbents designed for the specific affinity chromatography of sialidase in crude bacterial extracts

Purification and characterization of blood group A-degrading isoforms of alpha-N-acetylgalactosaminidase from Ruminococcus torques strain IX-70

To cleave blood group A immunodeterminants from erythrocytes (Hoskins, L. C., Larson, G., and Naff, G. B. (1995) Transfusion 35, 813-821), we purified and characterized alpha-N-acetylgalactosaminidase (EC 3.2.1.49) activity from culture supernatants of the human fecal bacterium Ruminococcus torques strain IX-70. Three isoforms separated during hydrophobic interaction chromatography. Hydroxyapatite chromatography further resolved the most hydrophilic, isoform I, into isoforms IA and IB. The most hydrophobic, isoform III, differed from IA and IB by a more acidic pH optimum, greater heat resistance, greater sensitivity to alkylating agents, and anomalous retardation during gel filtration chromatography. Isoform IB differed from IA and III in N-terminal amino acid sequence and in sensitivity to EDTA inhibition. Each cleaved nonreducing alpha(1-->3)-N-acetylgalactosamine residues from human blood group A and AB mucin glycoproteins, Forssman hapten, and blood group A lacto series glycolipids. The apparent molecular mass of denatured isoform subunits of IA, IB, and III-PII (158, 173, and 201 kDa, respectively) bore no integer relationship to the apparent molecular mass of the native isoforms (265, 417, and 530 kDa), but the latter bore a ratio of 1.96:3.09:3.93 to the weight-average apparent molecular mass of native IA (135 kDa), suggesting that the isoforms are multimers of a 135-kDa sequence. Isoforms IA and III-PII had an identical N-terminal amino acid sequence which showed homologies to the N-terminal sequence of sialidases produced by Bacteroides fragilis SBT3182, another commensal enteric bacterium.

Purification and properties of Arthrobacter neuraminidase

Neuraminidase (EC 3.2.1.18) from an Arthrobacter species was purified homogeneity by conventional procedures (yield approx. 1 mg/1) and was judged to be homogeneous by sodium dodecyl sulfate gel electrophoresis. Gel electrofocusing of neuraminidase revealed 1 major band (85-90%), pI 5.35 +/- 0.05, and 6 minor bands, whose pI ranged from 5.25 to 5.70, and each of which had catalytic activity. Arthrobacter neuraminidase is a monomeric glycoprotein of molecular weight 88 000, has an apparent Km of 7.8-10(-4) M for N-acetylneuraminlactose, is insensitive to inhibition by N-acetylneuraminic acid, and is about 2% carbohydrate by weight. The amino acid composition as well as the galactosamine and glucosamine content was determined. The enzyme can hydrolyze (alpha, 2-3), (alpha, 2-6), (alpha, 2-8) linkages. The active size of the enzyme appears to be inaccessible since no inhibition was observed by reagents known to modify sulfhydryl, lysyl, carboxyl, histidinyl, and argininyl residues. In contrast, N-bromosuccinimide at a 60-fold molar ratio to enzyme, gave complete inhibition. These results suggest that a tryptophan residue is essential for catalysis.

On the individuality of aliphatic and alicyclic monoester lipases in human adipose tissue

Aliphatic and alicyclic monoester lipase activities from human adipose tissue have been comparatively investigated by using [3H] oleoylethanol and [14C] oleoylcholesterol, respectively, as substrates. A number of specific properties proved to be different for each activity. Different rates of decay of hydrolytic activity towards each substrate were observed during heat denaturation. Stability upon exposure to the cold was different for both activities, and the protective effect of glycerol was less effective for oleoylcholesterol than for oleoylethanol lipase. Serial (NH4)2SO4 fractionation in 5% increments showed that the two activities did not precipitate at identical saturation values. The behaviours of the two activities were compared in an affinity system where monoolein, a substrate molecule, served as a ligand for the enzyme(s) in a covalent complex with CH-Sepharose. During chromatography, both activities followed a comparable adsorption-elution pattern, but the oleoylcholesterol to oleoylethanol lipase activity ratio decreased by a factor of 4. Taken together, these data, along with a differential susceptibility to various surfactants, confirm our earlier hypothesis (Arnaud, J. and Boyer, J (1974) Biochim. Biophys. Acta 337, 165--168) that aliphatic and alicyclic monoester lipase activities in human fat are referable to distinct catalytic proteins.