Mutarotase substrate specificities

Bentley and Bhate (66) described the properties of the enzyme isolated from P. notatum, and Wallenfels and Herrman have reported the isolation and substrate specificity of a mutarotase from E. coli (63). The widespread occurrence of the enzyme in higher plants (53), fish (69), birds (70) and amphibia (69) has been noted. Sacks has recently described the properties of the enzyme in human red blood cells (75). 

Table IV. Substrate Specificities of Mutarotases from Different Sources...

Mutarotation of 0.3% solutions of the freshly dissolved sugars in 12 ml of 5 mM EDTA, pH 7.4 was followed. Significant differences in mutarotation rates (AK) in the presence and absence of 100 units of bovine kidney enzyme were expressed as the ratio AK/Ksp. Differences of less than 5% in these rate constants were not considered significant. Of the 18 sugars listed, nine have been tested previously as substrates for other mammalian mutarotases with essentially the same pattern as described here. The pattern of specificity indicates that a 3-point attachment of enzyme and substrate is necessary for catalysis of mutarotation. b Data from 72). 

However, if these limitations are remembered, it can be instructive to compare the patterns of interaction which have been variously reported for substrates and inhibitors of mutarotase, with similar patterns for the kidney and intestinal sugar transport processes. In Table XIII the reported specificities for mammalian intestine are compared. In cases where comparative data are available, all sugars which are actively transported or which are passively transported but share the same carrier as glucose also interact with the active center of mutarotase. Particularly interesting is the observation that L-fucose, the most potent sugar inhibi-... 

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