Glucose-6-phosphatase physiology

In practice, using a normal chemistry panel and complete blood count it is not unusual to have 30 potential covariates, everything from sodium ion concentration to alkaline phosphatase activity. Early in PopPK analyses it was not unusual to screen every single covariate for their impact on the model. But a model might end up having a volume of distribution as a function of chloride ion concentration or clearance that is a function of glucose concentration. Physiologically, these covariates are nonsensical. Ideally at the end of model... 

N3. Nordlie, R. C., Some properties and possible physiological functions of phosphotransferase activities of microsomal glucose-6-phosphatase. Ann. N.Y. Acod. Sci. 166, 699-718 (1969). 

In chick embryos, sugar glucose and galactose are actively transported through the interstitial epithdium near the time of hatching and are accompanied by increases in alkaline phosphatase and succinic dehydrogenase in the villi. Similarly, some fundamental physiological functions do not develop until several months after birth. Infants renal function does not mature until four or even six months after birth before that, the kidney has below normal concentration ability-... 

Some physiological or pathological stimuli induce the liver cell to synthesize or break down some protein selectively. Even during starvation the content of all liver protein does not drop simultaneously. For example, while the activities of catalase, xanthine oxidase, alkaline phosphatase, and acid phosphatase drop at various rates as starvation progresses, that of glucose-6-phosphatase increases. Hydrocortisone and tryptophan administration induces a massive increase in tryptophan peroxidase activity. In either case, at least part of the increase in enzyme activity results from de novo enzyme synthesis. If tryptophan administration is interrupted, the activity of the peroxidase returns to normal. During the induction, turnover rates of other proteins do not change. 

The total number of polypeptides in the culture medium was 8-20 bands according to electrophoretic analysis (Figure 1). The protein export was inhibited by actinomycin D, cycloheximide, 2-deoxy-D-glucose and also by concanavalin A (Con A). In the presence of Con A (400 pg/ml), the enzymes were accumulated entirely inside the cells but not in the periplasm or the cell wall (Figure 2). At the same time the lectin had no influence upon cell growth and expression of invertase and acid phosphatase associated with the cell envelope. The activity accumulated inside Con A - treated cells was released into the culture medium on a-methylmannoside addition (Figure 3). The process was not affected by cycloheximide but was inhibited by sodium azide. The effect of Con A appears to be conditioned by its interaction with the plasma membrane of intact cells. Besides Con A, we detected peroxidase interaction with the plasmalemma of intact cells and alkaline phosphatase internment under physiological conditions. 

IV. Physiology of Glucose-6-phosphatase 1. Relation to Blood Glucose... 

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