The activities of fructose 1,6-diphosphatase, phosphofructokinase and phosphoenolpyruvate carboxykinase in white muscle and red muscle

Abstract

1. The activities of fructose 1,6-diphosphatase were measured in extracts of muscles of various physiological function, and compared with the activities of other enzymes including phosphofructokinase, phosphoenolpyruvate carboxykinase and the lactate-dehydrogenase isoenzymes. 2. The activity of phosphofructokinase greatly exceeded that of fructose diphosphatase in all muscles tested, and it is concluded that fructose diphosphatase could not play any significant role in the regulation of fructose 6-phosphate phosphorylation in muscle. 3. Fructosediphosphatase activity was highest in white muscle and low in red muscle. No activity was detected in heart or a deep-red skeletal muscle, rabbit semitendinosus. 4. The lactate-dehydrogenase isoenzyme ratio (activities at high and low substrate concentration) was measured in various muscles because a low ratio is characteristic of muscles that are more dependent on glycolysis for their energy production. As the ratio decreased the activity of fructose diphosphatase increased, which suggests that highest fructose-diphosphatase activity is found in muscles that depend most on glycolysis. 5. There was a good correlation between the activities of fructose diphosphatase and phosphoenolpyruvate carboxykinase in white muscle, where the activities of these enzymes were similar to those of liver and kidney cortex. However, the activities ofpyruvate carboxylase and glucose 6-phosphatase were very low in white muscle, thereby excluding the possibility of gluconeogenesis from pyruvate and lactate. 6. It is suggested that the presence of fructose diphosphatase and phosphoenolpyruvate carboxykinase in white muscle may be related to operation of the o-glycerophosphate-dihydroxyacetone phosphate and malate-oxaloacetate cycles in this tissue.The enzyme PFK$ (ATP-D-fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.11) in muscle has been shown to be a regulatory enzyme for glycolysis, and, on the basis of the properties of this enzyme, a theory for metabolic control has been proposed

Metabolic Differentiation of Distinct Muscle Types at the Level of Enzymatic Organization

“…Much lower incorporation rates were found in the case of white than of red muscles. These differences are consistent with the observed differences of hexokinase activity in the two muscle types, and corroborate indirectly the suggested function of gluconeogenesis in white (fast) muscle [22,35].…”

“…A main aspect is that of a quantitative coordination of mitochondrial glycerolphosphate dehydrogenase to the Embden-Meyerhof system with respect to the transfer of extramitochondrial ("glycolytic") hydrogen into the mitochondrial respiratory chain by means of the glycerolphosphate cycle [48,49]. An extension of this aspect consists in the suggestion [22,35] that the same system might furthermore function in providing triosephosphate from glycerolphosphate which accumulates during muscle work on the basis of glycerolphosphate -pyruvate dismutation [48--541. Triosephosphate would thus be supplied for the resynthesis of glucose or glycogen during the period of restitution. This assumption is in agreement with the constant activity ratio glycerolphosphate dehydrogenase/triosephosphate dehydrogenase, and is furthermore supported by the relatively high activities of hexosediphosphatase in white (fast) muscles.…”

“…The enzyme suspensions were centrifuged, the sedimented protein was dissolved in quartzdistilled water, and the solutions were treated with Sephadex G-25 (Pharmacia Fine Chemicals, Uppsala, Sweden). Activity determinations of hexosediphosphatase in crude extracts are complicated by the inhibitory effect of AMP [22,35,36]. I n order to remove AMP from the extracts, various methods were examined, e. g .…”

“…These differences are certainly not related to differences of species, but represent rather differences of muscle type. Thus, white (fast) muscles are characterized by high activities of extramitochondrial phosphorylase [8,9,16,19,21,24,25,27,28], triosephosphate dehydrogenase [7,13,[16][17][18]20,21,24,28], lactate dehydrogenase [7,[11][12][13][15][16][17][18]21,23,24] and by relatively high activities of mitochondrial glycerolphosphate dehydrogenase [9,[11][12][13]17,18,20,21] and extramitochondrial hexosediphosphatase [22,24,25]. On the other hand, red (slow) muscles show high activities of extramitochondrial hexokinase [21,, and of mitochondrial citrate synthase and 3-hydroxyacylCoA dehydrogenase [18,20,21,24,28].…”

Glycolytic and gluconeogenic enzyme activities in parenchymal and non-parenchymal cells from mouse liver

“…This was true even in experiments where 'L-type' pyruvate kinase was shown to be absent in this fraction. Although this activity may be due in part to non-specific phosphatase activity, it is probable that some true fructose 1,6-diphosphatase is indeed present, as has been shown, for example, in skeletal muscle (Opie & Newsholme, 1967). This is borne out by demonstration of the sensitivity of the enzyme to 5'-AMP added directly to the cuvette.…”