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.
Human α-mannosidases A, B and C were partially purified from liver by conventional
and affinity chromatographic procedures. The kinetic, physical and immunologic properties of the
A, B and C isozymes were determined including pH optima, K(m), effects of various inhibitors and
activators, thermal stabilities, electrophoretic mobilities, native molecular weights and antigenic
relationships.
By gel filtration, the apparent native molecular weights were 240,000, 300,000 and 420,000 for
the A, B and C isozymes, respectively. By polyacrylamide gel electrophoresis, the A and B
isozymes had native molecular weights of approximately 150,000 and appeared to be charge
isomers. Antibodies to the purified A and B isozymes were produced; cross-reactivity between the
A and B isozymes against anti-A and anti-B immune sera were observed by double immunodiffusion
and immunoprécipitation. In contrast, no reactivity of the C isozyme was detected with either
immune serum. Based on these studies, models are presented for the molecular interrelationship of
α-mannosidases A and B.
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