Phosphagens are phosphorylated guanidino compounds that are linked to energy state and ATP hydrolysis by corresponding phosphagen kinase reactions: phosphagen + MgADP + H(+) guanidine acceptor + MgATP. Eight different phosphagens (and corresponding phosphagen kinases) are found in the animal kingdom distributed along distinct phylogenetic lines. By far, the creatine phosphate/creatine kinase (CP/CK) system, which is found in the vertebrates and is widely distributed throughout the lower chordates and invertebrates, is the most extensively studied phosphagen system. Phosphagen kinase reactions function in temporal ATP buffering, in regulating inorganic phosphate (Pi) levels, which impacts glycogenolysis and proton buffering, and in intracellular energy transport. Phosphagen kinase reactions show differences in thermodynamic poise, and the phosphagens themselves differ in terms of certain physical properties including intrinsic diffusivity. This review evaluates the distribution of phosphagen systems and tissue-specific expression of certain phosphagens in an evolutionary and functional context. The role of phosphagens in regulation of intracellular Pi levels likely evolved early. Thermodynamic poise of the phosphagen kinase reaction profoundly impacts this capacity. Furthermore, it is hypothesized that the capacity for intracellular targeting of CK evolved early as a means of facilitating energy transport in highly polarized cells and was subsequently exploited for temporal ATP buffering and dynamic roles in metabolic regulation in cells displaying high and variable rates of aerobic energy production.

Evolution and physiological roles of phosphagen systems

Part 1 Overview of sea anemones: relationships and body plan the hydrostatic skeleton, muscles and mesoglea nervous system sensory receptors Cnidae why aren't there any colonial sea anemones?. Part 2 Nutrition: feeding extracellular digestion intracellular digestion translocation and storage symbiosis and unicellular algae photobiology. Part 3 Energy metabolism and respiratory gas exchange: cellular basis of glycolysis and aerobic respiration anaerobic energy metabolism rates of energy metabolism respiratory sunstrates and energetic equivalents of oxygen consumption gas exchange surfaces, their pemeabilty to oxygen and their ventilation factors affecting oxygen consumption. Part 4 Nitrogen excretion and osmotic balance: nitrogen excretion osmocomformity and cellular volume regulation water balance during aerial exposure. Part 5 Growth: units and measurement biochemical composition and energetic equivalents of body weight growth efficiency growth rate do sea anemones grow isometrically or allometrically? indeterminant growth and determinants of body size - the model environmental effects on growth and body size - the reality. Part 6 Reproduction and population structure: sexual reproduction asexual reproduction population structure. Part 7 Biotic interactions: competition ectosymbiosis predation on sea anemones. Appendix: classification of extant anthozoans, particularly sea anemones.

A Functional Biology of Sea Anemones

BACKGROUND Enzymatic and histochemical abnormalities of the peripheral muscle may play a role in exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). A study was undertaken to measure the mitochondrial enzyme activity of the vastus lateralis muscle in patients with COPD and to evaluate the relationship between enzyme activities and functional status.

METHODS Fifty seven patients with COPD of mean (SD) age 66 (7) years with forced expiratory volume in one second (FEV1) 39 (15)% predicted and peak oxygen uptake (V˙o 2) of 14 (4) ml/min/kg and 15 normal subjects of similar age were included in the study. Each subject performed a stepwise exercise test up to maximal capacity during which five-breath averages of V˙o 2were measured. Muscle specimens were obtained by percutaneous needle biopsy of the vastus lateralis muscle and the activity of two mitochondrial enzymes (citrate synthase (CS) and 3-hydroxyacyl CoA dehydrogenase (HADH)) was measured. The functional status of the patients was classified according to peakV˙o 2.

RESULTS CS and HADH activities were markedly reduced in patients with COPD compared with normal subjects (22.3 (2.7) versus 29.5 (7.3) μmol/min/g muscle (p<0.0001) and 5.1 (2.0) versus 6.7 (1.9) μmol/min/g muscle (p<0.005), respectively). The activity of CS decreased progressively with the deterioration in the functional status while that of HADH was not related to functional status. Using a stepwise regression analysis, percentage predicted functional residual capacity (FRC), the activity of CS, oxygen desaturation during exercise, age, and inspiratory capacity (% pred) were found to be significant determinants of peakV˙o 2. The regression model explained 59% of the variance in peak V˙o 2 (p<0.0001).

CONCLUSIONS The oxidative capacity of the vastus lateralis muscle is reduced in patients with moderate to severe COPD compared with normal subjects of similar age. In these individuals the activity of CS correlated significantly with peak exercise capacity and independently of lung function impairment.

https://thorax.bmj.com/content/thoraxjnl/55/10/848.full.pdf

Oxidative enzyme activities of the vastus lateralis muscle and the functional status in patients with COPD

The activities [units-1 wet weight tissue] of lactate dehydrogenase (LDH), pyruvate kinase (PK), malate dehydrogenase (MDH) and isocitrate dehydrogenase (IDH) in white skeletal muscle, brain and heart of 24 pelagic teleost fishes were determined. In addition, for several of the foregoing species, citrate synthase (CS) activities were examined in white skeletal muscle. In muscle, the activities of all these enzymes decrease exponentially with increasing minimum depth of occurrence of the species; this decrease closely parallels the decrease in respiratory rate found previously for these same species. The decline in enzymic activity with increasing minimum depth of occurrence is much greater than the decline in body protein content of the whole fishes, suggesting a disproportionately rapid fall in enzyme concentration in comparison to contractile and structural protein concentrations. The similar reductions in activities of both glycolytic (LDH and PK) and citric acid cycle (CS, MDH and IDH) enzymes with depth indicate that both standard and active metabolisms of deeper-dwelling species are reduced relative to shallower-dwelling forms. There is no suggestion of increased anaerobic capacity with depth or in relation to species, occurrence in the oxygen minimum layer. In brain and heart, there is no significant decrease in enzymic activity with increasing minimum depth of occurrence. These two tissues have similar capacities for metabolism in most fishes, when comparisons are based on enzymic activity per gram wet weight of tissue.

Depth-related enzymic activities in muscle, brain and heart of deep-living pelagic marine teleosts

Sustained exercise to fatigue elicits no major differences either in plasma amino acid levels or in brain 5-hydroxytryptamine (5-HT) metabolism between sedentary and endurance-trained animals. Furthermore, 11 weeks of endurance training did not influence the maximal activity of the enzyme monoamine oxidase in the brain areas which were studied. In both sedentary and endurance-trained rats, sustained running to fatigue caused an increase in the plasma concentration ratio of free tryptophan/other large neutral amino acids and an increase in the concentration of tryptophan in the six brain areas that were studied. The increase was similar in the different regions of the brain and averaged 36%. Exercise caused an increase in the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the brain stem (14 and 44% respectively) and hypothalamus (16 and 17% respectively) and an increase in the level of 5-HIAA in the hippocampus (21%) and striatum (28%). Exercise also caused an increase in the level of dopamine in the brain stem (56%) and hypothalamus (46%) and of nor adrenaline in the striatum (59%). Since the levels of 5-HT and dopamine were both increased in the brain stem and hypothalamus, it is possible that these changes may play important roles in the central effects of exercise, including both physical and mental fatigue and effects on mood.

Effect of sustained exercise on plasma amino acid concentrations and on 5-hydroxytryptamine metabolism in six different brain regions in the rat.

Comparison of the activities of hexokinase, phosphorylase and phosphofructokinase in muscles from marine invertebrates indicates that they can be divided into three groups. First, the activities of the three enzymes are low in coelenterate muscles, catch muscles of molluscs and muscles of echinoderms; this indicates a low rate of carbohydrate (and energy) utilization by these muscles. Secondly, high activities of phosphorylase and phosphofructokinase relative to those of hexokinase are found in, for example, lobster abdominal and scallop snap muscles; this indicates that these muscles depend largely on anaerobic degradation of glycogen for energy production. Thirdly, high activities of hexokinase are found in the radular muscles of prosobranch molluscs and the fin muscles of squids; this indicates a high capacity for glucose utilization, which is consistent with the high activities of enzymes of the tricarboxylic acid cycle in these muscles [Alp, Newsholme & Zammit (1976) Biochem. J. 154, 689-700]. 2. The activities of lactate dehydrogenase, octopine dehydrogenase, phosphoenolpyruvate carboxykinase, cytosolic and mitochondrial glycerol 3-phosphate dehydrogenase and glutamate-oxaloacetate transaminase were measured in order to provide a qualitative indication of the importance of different processes for oxidation of glycolytically formed NADH. The muscles are divided into four groups: those that have a high activity of lactate dehydrogenase relative to the activities of phosphofructokinase (e.g. crustacean muscles); those that have high activities of octopine dehydrogenase but low activities of lactate dehydrogenase (e.g. scallop snap muscle); those that have moderate activities of both lactate dehydrogenase and octopine dehydrogenase (radular muscles of prosobranchs), and those that have low activities of both lactate dehydrogenase and octopine dehydrogenase, but which possess activities of phosphoenolpyruvate carboxykinase (oyster adductor muscles). It is suggested that, under anaerobic conditions, muscles of marine invertebrates form lactate and/or octopine or succinate (or similar end product) according to the activities of the enzymes present in the muscles (see above). The muscles investigated possess low activities of cytosolic glycerol 3-phosphate dehydrogenase, which indicates that glycerol phosphate formation is quantitatively unimportant under anaerobic conditions, and low activities of mitochondrial glycerol phosphate dehydrogenase, which indicates that the glycerol phosphate cycle is unimportant in the re-oxidation of glycolytically produced NADH in these muscles under aerobic conditions. Conversely, high activities of glutamate-oxaloacetate transaminase are present in some muscles, which indicates that the malate-aspartate cycle may be important in oxidation of glycolytically produced NADH under aerobic conditions. 3. High activities of nucleoside diphosphate kinase were found in muscles that function for prolonged periods under anaerobic conditions (e.g...

The maximum activities of hexokinase, phosphorylase, phosphofructokinase, glycerol phosphate dehydrogenases, lactate dehydrogenase, octopine dehydrogenase, phosphoenolpyruvate carboxykinase, nucleoside diphosphatekinase, glutamate-oxaloacetate transaminase and arginine kinase in relation to carbohydrate utilization in muscles from marine invertebrates.

E A Newsholme

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