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N-acetyl-beta-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.

SUBMITTER: Ikonne JU

PROVIDER: S-EPMC1165847 | biostudies-other | 1973 Nov

REPOSITORIES: biostudies-other

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Project description:Mucolipidosis III acid hydrolases possess an altered carbohydrate recognition marker needed for their lysosomal localization. As a result of this alteration, a portion of these enzymes is secreted from the cell to the extracellular spaces. The structural changes that may have occurred to one of these secreted enzymes, beta-N-acetyl-d-hexosaminidase A (EC 3.2.1.52) were investigated. Normal and mucolipidosis III urinary beta-N-acetyl-d-hexosaminidase A were purified to apparent homogeneity by using affinity [Sepharose-2-acetamido-N-(epsilon-aminocaproyl)-2-deoxy-beta- d-glucopyranosylamine] and ion-exchange (DEAE- and CM-cellulose) chromatography. Sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis showed that both enzymes had similar subunit patterns consisting of apparent mol.wts. of 68000, 60000-58000, 55000 and 29000. Differences, however, were noted in the relative proportions of the protein bands where the normal urinary beta-N-acetyl-d-hexosaminidase A contained predominantly the smaller subunits, whereas the mucolipidosis III enzyme had a predominance of the larger subunits. The binding of mucolipidosis III beta-N-acetyl-d-hexosaminidase A to Ricinus communis lectin and concanavalin A with and without endo-beta-N-acetyl-d-glucosaminidase H treatment indicated that the mutation leads to a modification of a portion of the normally occurring high-mannose-type oligosaccharide units to the complex-type. This was further supported by carbohydrate compositional analysis, which revealed a mannose/galactose ratio of 2.1 for the mucolipidosis III beta-N-acetyl-d-hexosaminidase A compared with a ratio of 3.5 for the normal enzyme. Our results indicate that as a result of their inability to be properly localized to the lysosome the majority of the mucolipidosis III lysosomal hydrolase high-mannose oligosaccharide units are further processed to the complex-type before secretion of predominantly higher-molecular-weight subunits from the cell.

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N-acetyl-beta-D-hexosaminidase component A. Different forms in human tissues and fluids.

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