[Localization of the degradation of injected maltose]

The major maltase activity was found in the kidneys, followed by liver, muscle and blood. Only low maltase activity has been found in adipose tissue, muscle, and brain. The pH-optimum of kidney maltase was at pH = 6.0, the Michaelis-Menten Constant was measured to be 15.6 X 10(-3) mol/l. Even with a dose of 200 mg maltose/100 g body weight saturation of the hydrolysing system could not be attained in living rats. In nephrectomized rats the maltose oxidation was reduced to 55%. Only 0.2% of the applied maltose is excreted into the bile. According to our results the following main pathway of metabolism of maltose is suggested: glomerular filtration of maltose, hydrolysis of maltose to glucose by maltases which are localized in the membrane of the kidney brush borders, absorption of glucose, oxidation of glucose to CO2. In addition an extrarenal maltase activity is considered in the liver. The metabolism of injected trehalose was only 10% when compared with the metabolism of maltose.