N-Acetyl-β-d-hexosaminidase component A. Different forms in human tissues and fluids

Abstract

1. Hexosaminidase A of human serum was resolved into two components, a minor form with properties identical with those of the single hexosaminidase A component of human liver, and a major form with significantly different properties. 2. The major serum hexosaminidase A form was eluted from a DEAE-cellulose column at a lower salt concentration than that required to elute the liver form. 3. A multiple-pass technique was used to elute the major serum enzyme A from a Sephadex G-150 column before that of liver enzyme A. 4. Clostridium perfringens neuraminidase converted the major component of serum hexosaminidase A into a form that was held less tightly by DEAE-cellulose, but the minor component of the A enzyme of serum, and the A enzyme of liver were not affected. 5. The hexosaminidase A from tears was similar to the A enzyme from serum, whereas those from several human tissues and from urine and lymph were similar to the liver form. 6. The A enzyme from serum may be derived from the A enzyme from liver by glycosylation before secretion.

I-cell disease (mucolipidosis II): Resolution of N-acetyl-β-d-glucosaminidase and α-l-fucosidase components by DEAE-cellulose chromatography

“…2a) were similar to those previously reported for human brain, liver and other tissues (Ikonne & Ellis, 1973). Extracts of fibroblasts from all three patients with I-cell disease had lowered total glucosaminidase activities, similar to those reported for other cases (Leroy et al, 1972;Wiesmann & Herschkowitz, 1974).…”

“…l b and Id). Components I,, It and A were greatly reduced, there was an increased activity of component(s) not retained by the column, and a new form was noted, which was eluted slightly later than I2 (Ikonne & Ellis, 1973). However, appreciable activity of an intermediate form with a peak maximum at 14 min was seen only in the neuraminidase-treated I-cell disease plasma (Fig.…”

“…Neuraminidase caused no detectable change in the other form of component A even after prolonged treatment. This form of glucosaminidase thus behaved like the minor A component of serum or plasma and the form present in tissues (Ikonne & Ellis, 1973). Though different proportions of serum-type to tissue-type glucosaminidase A were found in medium from different cultures of normal cells, the tissue form always predominated (60-90% of A activity, estimated from peak areas after neuraminidase treatment).…”

Interrelationship of hexosaminidases A and B: conformation of the common and the unique subunit theory.

“…In fact, all six isozymes are present in normal human liver and kidney (Fig. 5) (32)(33)(34)(35)(36).…”

Design and synthesis of 4′-O-alkyl-chitobiosyl-4-methylumbelliferone as human chitinase fluorogenic substrates

“…For instance, b-hexosaminidases may in a stepwise fashion remove a GluNAc moiety from the non-reducing end, resulting in undesired background release of 4-MU. 15 Therefore, the ability of jack bean (Canavalia) b-hexosaminidase to sequentially hydrolyse the modified 4-MU-chitobioses was examined. As a benchmark, jack bean b-hexosaminidase enzymatic activity towards 4-MU-GlcNAc (0.135 mM) was first determined at the optimal pH of 4.0.…”