Inhibition by Glycerol

Glycerol absorption in H. diminuta occurs by passive diffusion at high concentrations (>0.5mM) and by a carrier-mediated process at lower concentrations. At lower concentrations, absorption of this lipid precursor is non-linear, dependent on temperature and pH, and competitively inhibited by glycerol and a-glycerophosphate. The existence of two distinct carriers for this molecule is suggested by studies which show that only about half the saturable component in H. diminuta is Na -sensitive and inhibitable by 1,2-propandiol (2). 

Both the Ca2 -dependent and Mg2+-dependent ATPases are inhibited by ADP (apparently allosterically), phlorizin, and antisera directed against the native spinach CF] and native CrCF]. Whereas the Ca " -dependent ATPase is severely inhibited by glycerol (I50 ca. 8%, v/v) and NaCI (I q ca. 100 mM), the Mg " "-dependent ATPase is not. Neither DCF] ATPase activity is inhibited by antisera directed against the individual SDS-denatured subunits of CrCF]. 

Sulphites react with molecular oxygen (or air) to give sulphates, a reaction catalysed by certain ions (for example Fe, Cu, arsenate(III) ion, AsO ) and inhibited by, for example, phenol, glycerol and tin(II) ions, Sn ... 

Figure 25-7. Metabolism of adipose tissue. Hormone-sensitive lipase is activated by ACTH, TSH, glucagon, epinephrine, norepinephrine, and vasopressin and inhibited by insulin, prostaglandin E, and nicotinic acid. Details of the formation of glycerol 3-phosphate from intermediates of glycolysis are shown in Figure 24-2. (PPP, pentose phosphate pathway TG, triacylglycerol FFA, free fatty acids VLDL, very low density lipoprotein.)...

Furthermore, the LPS signal transduction involves the activation of G proteins, of phospholipases C and D, the formation of diacyl-glycerol (DG) and inositol triphosphate (IP3). DG mediates the stimulation of protein kinase C (PKC) and IP3 induces an increase of cytosolic Ca++ The LPS signaling pathway also involves tyrosine kinases, constitutive nitric oxide (NO) synthase (cNOS), cGMP-dependent protein kinase, Ca channels, calmodulin and calmodulin kinase [27,28], as well as the MAP kinases [29] ERK1, ERK2 and p38 [23], The intracellular events in response to LPS are due to lipid A because they are inhibited by polymyxin B which is known to bind lipid A [27] and they are reproduced by lipids A [30,31]. 

B-type esterases (glycerol tricarboxyl esterases, aliphatic esterases, lipases EC 3.1.1.3) they are most active on aliphatic esters although they show some activity on aromatic esters they are inhibited by organophosphates. 

When lipids are required by the body for energy, adipose cell hormone-sensitive lipase (activated by epinephrine, and inhibited by insulin) initiates degradation of stored triacyl glycerol. 

The poly (ribitol phosphate) synthetase and poly (glycerol phosphate) synthetase are inhibited by vancomycin, novobiocin, and Crystal Violet. Other antibiotic substances which interfere with cell-wall synthesis (such as bacitracin, ristocetin, and streptomycin) are almost without effect on the isolated synthetases, and penicillin is inhibitory at high concentrations only. Moreover, penicillin, vancomycin, and bacitracin do not markedly inhibit synthesis of cell-wall glycosaminopeptide in vitro, although the synthetical activity of extracts of cells which have been pretreated with these antibiotics is lowered.Convincing evidence that the primary site of inhibition by antibiotics is the biosynthesis of cell-wall material has been obtained only for the penicillins and cycloserine, and it appears that the action of even those antibiotics may be more complex than was originally supposed. 

L. G. Lee and G. M. Whitesides, Preparation of optically active 1,2-diols and a-hydroxy ketones using glycerol dehydrogenase as catalyst limits to enzyme-catalyzed synthesis due to noncompetitive and mixed inhibition by product, J. Org. Chem. 1986, 51, 25-36. 

Fig. 10.6. The effect of respiration and membrane potential (Ai )) on Cl permeation in brown adipose tissue mitochondria. When brown fat mitochondria were incubated in KCl in the presence of the ionophore, nigericin, they swelled (A, B). If a respiratory substrate (here G-3-P glycerol-3-phosphate) was added to the expanded mitochondria, they contracted, and this contraction ceased immediately and swelling was reintroduced if azide (NaNj) and an uncoupler (FCCP) were added (Fig. A). The passive halide ion permeability can be inhibited by GDP (cf.. Fig. 10.5), but respiration-driven contraction in KCl-expanded mitochondria was only partially inhibited by the presence of GDP (Fig. B) if again azide and uncoupler were added during the contraction, the mitochondria did not swell, indicating that the thermogenin channel was closed by GDP. This behaviour can partly be explained by the fact that the Cl permeation is driven by the membrane potential. Indeed, when, under similar conditions, the rate of contraction was plotted as a function of the membrane potential, it was seen that the rate was membrane potential dependent. It should, however, he noted that at low membrane potentials GDP nearly totally abolished the Cl permeation but when the membrane potential was increased above 30 mV, the inhibitory effect of GDP was apparently partially lost. The basis for this phenomenon is not understood it is not even known if there is a lower affinity of thermogenin for GDP in the energized membrane, as measurements of GDP affinities always refer to the non-energized situation. (Adapted from Nicholls et al. [27] (A, B) and Nicholls [94] (C).)...

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