Galactose accumulation

The proteinuria and aminoaciduria, and acidosis and glucosuria where they occur, are probably caused by reversible inhibition of some functions of the renal tubule. There would appear to be no structural damage to the kidney. However, 2 children developed nephrolithiasis while being treated with a low-lactose diet (B7, C5), The time course of events, when galactose is withdrawn from and returned to the diet, suggests that some metabolite of galactose accumulates in the cells of the renal tubules and has an inhibitory effect on the reabsorption of a number of substances. 

Galactose 1-phosphate uridyltransferase is missing in individuals with classic galactosemia (see Figure 12.5). In this disorder, galac tose 1-phosphate and, therefore, galactose, accumulate in cells. 

Answer In galactokinase deficiency, galactose accumulates in UDP-glucose galactose 1-phosphate uridylyltransferase deficiency, galactose 1-phosphate accumulates (see Fig. 14-12). The latter metabolite is clearly more toxic. 

The metabolism of lactose and lactate in Swiss-type cheeses was described comprehensively by Turner et al. (1983). Typically, Emmental cheese contains 1.7% lactose 30 min after moulding, which is rapidly metabolized by 5. thermophilus with the production of L-lactate. Only the glucose moiety of lactose is metabolized by S. thermophilus and consequently galactose accumulates to a maximum of —0.7% at —10 hr, when the lactobacilli begin to multiply. These metabolize galactose to a mixture of d- and L-lactate, which reach —0.35 and 1.2%, respectively, at 14 days, when the galactose is metabolized completely. 

Galactosemia Defective transferase resulting in poor metabolism of galactose accumulation of galactose in cells causes cataracts and mental retardation. 

Fig. 1. Zero trans uptake of galactose by human red blood cells at 20 C. Time course of uptake from a solution containing 250 mM galactose in a salt medium to a total osmolarity of 560 mosM/1. The inset shows the very early portion of the uptake curve. The overall curve is linear at such short times but becomes more and more curved as galactose accumulates within the cell. (Data taken, with permission, from [33].)...

A disease with similar symptoms occurs in galactokinase deficiency. In both cases, galactose accumulates and it is reduced to galactitol by aldose reductase. 

In the Swiss variant , better termed galactokinase deficiency, reaction 1 is blocked [24]. Hence galactose accumulates but Gal-l-P does not. Galactose and galactitol are... 

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