Gene dosage effect in human triploid fibroblasts

Summary The activity of 13 cytoplasmic enzymes has been determined in fibroblast extracts from 9 triploid and 13 control lines. The results show a high activity for 2 X-linked enzymes, glucose 6-phosphate dehydrogenase and phosphoglycerate kinase. These data, together with cytogenetic observations, support the contention that 2 X chromosomes were active in the triploid lines.Abbreviations G6PD Glucose 6-phosphate dehydrogenase - 6PGD 6-phosphogluconate dehydrogenase - HK hexokinase - PGM phosphoglucomutase - PHI phosphohexoisomerase - PFK phosphofructokinase - ALD aldolase - TPI triosephosphate isomerase - PGK phosphoglycerate kinase - ENOL enolase - AK adenylate kinase - LDH lactic dehydrogenase - HBDH hydroxybutyrate dehydrogenase INSERM U. 129.INSERM U. 73.     

Steroid synthesizing cellular sites in the ovary of the domestic pigeon Columba livia (Gmelin): a histochemical study.

Synopsis The ovary of the domestic pigeon,Columba livia, has been assayed histochemically for the localization of ⁵-3-hydroxysteroid dehydrogenase (⁵-3-HSDH), 17-hydroxysteroid dehydrogenase (17-HSDH), 11-hydroxysteroid dehydrogenase (11-HSDH), glucose-6-phosphate dehydrogenase (G6P-DH) and NADH-diaphorase activities during different periods of the reproductive cycle. ⁵-3-HSDH, 17-HSDH, 11-HSDH, G6P-DH and NADH-diaphorase activity was found in the theca interna of growing, atretic and postovulatory follicles, the granulosa of ovulatory, atretic and postovulatory follicles, and interstitial gland cells during the pre-incubation and the laying periods. During the incubation and squab feeding periods only ⁵-3-HSDH, G6P-DH and NADH-diaphorase activities were observed in the above mentioned cells. The steroidogenic potential of atretic follicles depends upon the type of atresia a follicle undergoes.     

Histochemical comparison of oxidative enzymes in adrenal glands of mammals

Summary Succinic dehydrogenase, five DPN-linked dehydrogenases-lactic dehydrogenase, malic dehydrogenase, glutamic dehydrogenase, -glycerophosphate dehydrogenase, -hydroxybutyric dehydrogenase, two TPN linked dehydrogenases — glucose-6-phosphate dehydrogenase, isocitric dehydrogenase and 3-ol steroid dehydrogenase were studied in mouse, rat, guinea pig, rabbit, dog, cat, cow, monkey and human adrenal glands. Histochemical studies were made of a characteristic distribution of different level of enzyme activity. In mammals adrenal glands, glucose-6-phosphate dehydrogenase showed the highest activity and its localization was divided into the following two groups: 1) High enzymatic activity was demonstrated in the zona fasciculata and reticularis of the rat, guinea pig, rabbit, cat and 2) high enzymatic activity was demonstrated in the zona glomerulosa and reticularis of the dog, cow and monkey. A precise relationship between the localization and endocrinological function remains abscure.     

Enzyme histochemical studies on rat lungs 2. Normal enzyme distribution in the alveolar tissue of the mature lung

Synopsis The activity and distribution of the following eighteen oxidative and hydrolytic enzyme systems have been investigated in the lung of the adult rat: reduced NAD dehydrogenase, reduced NADP dehydrogenase, succinate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose dehydrogenase, glutamate dehydrogenase, -hydroxybutyrate dehydrogenase, acid phosphatase, alkaline phosphatase, glucose-6-phosphatase, adenosine triphosphatase, 5-nucleotidase, non-specific esterase, cytochrome oxidase and -glucuronidase.The low concentration of cells in sections of inflated lung may have made histochemical demonstration of some enzymes impossible because the enzyme concentration was below that detectable by the method employed.The carboxylic acid cycle and the hexose monophosphate shunt were potentially active but fatty acid metabolism was not indicated.The granular reaction sometimes encountered in alveolar cell cytoplasm may be useful for differentiating alveolar cell types, but further cytochemical studies are required to resolve the possible metabolic differences of alveolar cells.     

Production of active human interferon-β inE. coli I. Preferential production by lower culture temperature

Summary Unusually low culture temperature, such as 20°C, was shown to be preferable for the synthesis of active human interferon- (IFN-) inE. coli harboring a recombinant plasmid. TheE. coli cells cultured at 20°C gave 8.6-fold higher IFN- activity than those cultured at 37°C. However, almost the equal amounts of IFN- protein were accumulated in both cells cultured at 20°C and at temperature higher than 20°C, suggesting that IFN- might exist as an active form in the cells cultured at 20°C, while as a rather denatured form in the cells cultured at higher temperature.     

Enzymes and pathways of glucose utilization in bovine adrenal medulla

Glucose utilization by different metabolic pathways in bovine adrenal medulla has been studied using freshly isolated adrenal chromaffin cells. The rate of net glucose utilization in resting cells was 10.5 moles × g^–1 × h^–1 50% was transformed into lactate and pyruvate, the lactate to pyruvate ratio ranging from 3 to 7. 27% was metabolized through the tricarboxylic acid cycle and 3.1% was oxidized in the pentose phosphate pathway. The ratio of ¹⁴CO₂ production from 11-¹⁴Cl glucose and 16-¹⁴Cl glucose was close to 2 at one hour of incubation. 3.210 of total glucose consumed was used in protein synthesis, and 1% was incorporated into lipids. Oxygen utilization in respiration by isolated adrenal chromaffin cells was 18.2 moles × g^–1 × h^–1, corresponding to 3.1 moles glucose × g^–1 × h^–1 or about 30°10 of total glucose consumed. The activities of hexokinase, enolase, pyruvate kinase, lactate dehydrogenase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were assayed in extracts of bovine adrenal medulla, being 1.0, 23, 40, 37, 6.0 and 3.0 U/g respectively. Hexokinase activity was identified as belonging mainly to isoenzyme I, with some isoenzyme II. Enolase was predominantly the hybrid. Pyruvate kinase activity corresponded to a mixture of isoenzymes K and M. Lactate dehydrogenase activity corresponded to isoenzymes 1, 2 and 3, with smaller proportions of isoenzymes 4 and 5. Results are discussed mainly with respect to those reported for the brain.Abbreviations NBT nitro blue tetrazolium - PEP phesphoenolpyruvate - PMS phenazine methosulfate - U unit of enzyme activity     

Effects of 17β-estradiol on the distribution and activity of some oxydative enzymes of uterine and cervical epithelium in neonatal mice

Summary The following enzymes were studied histochemically in uterine and cervical epithelium from neonatal mice treated with 17-estradiol for the first four days after birth: NADH-, NADPH-, succinate-, -glycerophosphate-, lactate-, glucose-6-phosphate-, and 17-OH-steroid dehydrogenases.It was demonstrated that estradiol administration had a marked influence on distribution and activity of several of the enzymes compared with the control animals. In cervix there was an increase of activity for most of the enzymes, especially in the apical parts of the epithelium cells. The uterine epithelium was also estradiol sensitive as regards most enzymes, and in the case of glucose-6-phosphate dehydrogenase there was a dramatic enhancement of reaction in the uterus of the experimental animals. The differences obtained between cervical and uterine epithelium are described.17-OH-steroid dehydrogenase could not be detected histochemically in the present material.Supported by the Norwegian Research Council for Science and the Humanities.     

Protection against UVB inactivation (in vitro) of rat lens enzymes by natural antioxidants

Oxidative damage, through increased production of free radicals, is believed to be involved in UV-induced cataractogenesis (eye lens opacification). The possibility of UVB radiation causing damage to important lenticular enzymes was assessed by irradiating 3 months old rat lenses (in RPMI-1640 medium) at 300 nm (100 Wcm-2) for 24 h, in the absence and presence of ascorbic acid, -tocopherol acetate and -carotene. UVB irradiation resulted in decreased activities of hexokinase, glucose-6-phosphate dehydrogenase, aldose reductase, and Na, K- ATPase by 42, 40, 44 and 57% respectively. While endopeptidase activity (229%) and lipid peroxidation (156%) were increased, isocitrate dehydrogenase activity was not altered on irradiation. In the presence of externally added ascorbic acid, tocopherol and -carotene (separately) to the medium, the changes in enzyme activities (except endopeptidase) and increased lipid peroxidation, due to UVB exposure, were prevented. These results suggest that UVB radiation exerts oxidative damage on lens enzymes and antioxidants were protective against this damage.     

Cellular and Subcellular Localization of Hexokinase, Glutamate Dehydrogenase, and Alanine Aminotransferase in the Honeybee Drone Retina

Abstract: Subcellular localization of hexokinase in the honeybee drone retina was examined following fractionation of cell homogenate using differential centrifugation. Nearly all hexokinase activity was found in the cytosolic fraction, following a similar distribution as the cytosolic enzymatic marker, phosphoglycerate kinase. The distribution of enzymatic markers of mitochondria (succinate dehydrogenase, rotenone-insensitive cytochrome c reductase, and adenylate kinase) indicated that the outer mitochondrial membrane was partly damaged, but their distributions were different from that of hexokinase. The activity of hexokinase in purified suspensions of cells was fivefold higher in glial cells than in photoreceptors. This result is consistent with the hypothesis based on quantitative 2-deoxy[³H]glucose autoradiography that only glial cells phosphorylate significant amounts of glucose to glucose-6-phosphate. The activities of alanine aminotransferase and to a lesser extent of glutamate dehydrogenase were higher in the cytosolic than in the mitochondrial fraction. This important cytosolic activity of glutamate dehydrogenase was consistent with the higher activity found in mitochondria-poor glial cells. In conclusion, this distribution of enzymes is consistent with the model of metabolic interactions between glial and photoreceptor cells in the intact bee retina.     

The ultrastructural localization of the enzymes related to steroid hormone metabolism in the guinea-pig testis

Synopsis A study of the ultrastructural localization of 3-hydroxysteroid dehydrogenase (3-HSD), 11-hydroxysteroid dehydrogenase (11-HSD), glucose-6-phosphate dehydrogenase (G-6-PD), -hydroxybutyrate dehydrogenase (-HBD), NADH diaphorase (NADH-D) and NADPH diaphorase (NADPH-D) in the guinea-pig testis is reported.The procedures employed included short immersion or perfusion fixation with aldehydes followed by incubation of small blocks in a tetrazolium salt or a ferricyanide medium. The effects of incubation conditions were investigated, and a reaction medium for the ultracytochemical demonstration of 11-HSD is described. Using suitable controls, evidence for the specificity of the cytochemical reactions is presented.It was found that all the enzymes studied were present in both the Leydig and Sertoli cells of the guinea-pig testis and that the intracellular distribution pattern for each enzyme was independent of the cell type. Using tetrazolium salt techniques, both 3-HSD and 11-HSD activities were localized on or in membranes of smooth endoplasmic reticulum and within the mitochondria. With the ferricyanide techniques, G-6-PD activity was found to be associated mainly with the smooth endoplasmic reticulum membranes, while -HBD activity was limited to mitochondria. With both the tetrazolium salt and ferricyanide techniques, the reaction products for NADH-D and NADPH-D activities showed localizations which were similar to those observed for the steroid dehydrogenases.     

A comparative histochemical evaluation of various dehydrogenases in the oral squamous epithelium

Summary A histochemical observation was made of various dehydrogenase activities in oral squamous epithelia. The localization of dehydrogenases showed a relatively similiarity except for the intensity of the dehydrogenase activity. Succinic dehydrogenase activity was generally confined to the basal cell layer and adjacent cell layers; superficial layers did not show any enzymatic activity. Lactic, and malic dehydrogenase activities were localized in the basal cells to st. granulosum, and the activity of lactic dehydrogenase was the highest. -Glycerophosphate, glutamic, glucose-6-phosphate and TPN-isocitric dehydrogenase activities were observed in all the epithelial cells with the exception for the hornified layer, and they were found generally low. -Hydroxybutyric dehydrogenase was low and contained in both of st. germinativum and st. granulosum, the keratohyalin in st. granulosum being occasionally found reactive to this enzymatic activity.In connective tissue cells and collagen bundels, activities of lactic, and malic dehydrogenase were intense, while other dehydrogenases were low or trace amount.In the oral squamous epithelium under normal conditions, the dehydrogenase localization concerning the glucose metabolism and TCA cycle member and other close pathways was not similar. Nor were their activities found likewise. Those findings lead to a conclusion that the epithelial cells of the same layer many show a selective metabolic activity.With 21 Figures in the Text     

Assaying for pyruvate,orthophosphate dikinase activity: Necessary precautions with phosphoenolpyruvate carboxylase as coupling enzyme

Phosphoenolpyruvate carboxylase (EC 4.1.1.31), used as a coupling enzyme in the assay of the pyruvate, orthophosphate dikinase (EC 2.7.9.1) forward reaction, is a serious limiting factor for the overall rate when added at a level of 0.2–0.3 unit/ml of assay medium. Nonlimiting assay conditions are obtained by either increasing the level of the coupling enzyme to 3 units/ml or adding 6mM glucose-6-phosphate as an activator/stabilizer of phosphoenolpyruvate carboxylase.Abbreviations G-6-P glucose-6-phosphate - LDH lactate dehydrogenase - MDH malate dehydrogenase - PEP phosphoenolpyruvate - PEPCase phosphoenolpyruvate carboxylase - PVP polyvinylpyrrolidone - PPDK pyruvate, orthophosphate dikinase - U unit of enzyme activity (mol/min)     

Development of mitochondrial energy metabolism in rat brain

1. The development of pyruvate dehydrogenase and citrate synthase activity in rat brain mitochondria was studied. Whereas the citrate synthase activity starts to increase at about 8 days after birth, that of pyruvate dehydrogenase starts to increase at about 15 days. Measurements of the active proportion of pyruvate dehydrogenase during development were also made. 2. The ability of rat brain mitochondria to oxidize pyruvate follows a similar developmental pattern to that of the pyruvate dehydrogenase. However, the ability to oxidize 3-hydroxybutyrate shows a different developmental pattern (maximal at 20 days and declining by half in the adult), which is compatible with the developmental pattern of the ketone-body-utilizing enzymes. 3. The developmental pattern of both the soluble and the mitochondrially bound hexokinase of rat brain was studied. The total brain hexokinase activity increases markedly at about 15 days, which is mainly due to an increase in activity of the mitochondrially bound form, and reaches the adult situation (approx. 70% being mitochondrial) at about 30 days after birth. 4. The release of the mitochondrially bound hexokinase under different conditions by glucose 6-phosphate was studied. There was insignificant release of the bound hexokinase in media containing high KCl concentrations by glucose 6-phosphate, but in sucrose media half-maximal release of hexokinase was achieved by 70μm-glucose 6-phosphate 5. The production of glucose 6-phosphate by brain mitochondria in the presence of Mg²⁺+glucose was demonstrated, together with the inhibition of this by atractyloside. 6. The results are discussed with respect to the possible biological significance of the similar developmental patterns of pyruvate dehydrogenase and the mitochondrially bound kinases, particularly hexokinase, in the brain. It is suggested that this association may be a mechanism for maintaining an efficient and active aerobic glycolysis which is necessary for full neural expression.     

Evidence for a higher glycolytic than oxidative metabolic activity in white matter of rat brain

Different values exist for glucose metabolism in white matter; it appears higher when measured as accumulation of 2-deoxyglucose than when measured as formation of glutamate from isotopically labeled glucose, possibly because the two methods reflect glycolytic and tricarboxylic acid (TCA) cycle activities, respectively. We compared glycolytic and TCA cycle activity in rat white structures (corpus callosum, fimbria, and optic nerve) to activities in parietal cortex, which has a tight glycolytic-oxidative coupling. White structures had an uptake of [(3)H]2-deoxyglucose in vivo and activities of hexokinase, glucose-6-phosphate isomerase, and lactate dehydrogenase that were 40-50% of values in parietal cortex. In contrast, formation of aspartate from [U-(14)C]glucose in awake rats (which reflects the passage of (14)C through the whole TCA cycle) and activities of pyruvate dehydrogenase, citrate synthase, alpha-ketoglutarate dehydrogenase, and fumarase in white structures were 10-23% of cortical values, optic nerve showing the lowest values. The data suggest a higher glycolytic than oxidative metabolism in white matter, possibly leading to surplus formation of pyruvate or lactate. Phosphoglucomutase activity, which interconverts glucose-6-phosphate and glucose-1-phosphate, was similar in white structures and parietal cortex ( approximately 3 nmol/mg tissue/min), in spite of the lower glucose uptake in the former, suggesting that a larger fraction of glucose is converted into glucose-1-phosphate in white than in gray matter. However, the white matter glycogen synthase level was only 20-40% of that in cortex, suggesting that not all glucose-1-phosphate is destined for glycogen formation.     

Steroid dehydrogenases in the adrenal gland of four species of birds: a histochemical study

Synopsis The presence of⁵-3-hydroxysteroid dehydrogenase, II-hydroxysteroid dehydrogenase, 17-hydroxysteroid dehydrogenase and glucose-6-phosphate dehydrogenase has been demonstrated histochemically in the adrenal gland of the rain quailCoturnix coromendalica, barn owlTyto alba, brown crakeAmaurornis akool and painted partidgeFrancholinus pictus. All these enzymes occurred in the inter-renal cells. No activity was observed in the chromaffin cells. It is suggested that the inter-renal cells of these four species of birds are capable of synthesizing both corticosteroids and sex steroids.     

A preliminary note on the hormonal induction of NADP-linked dehydrogenases in phytohaemagglutinin-stimulated human lymphocytes

Synopsis Human leucocytes were culturedin vitro with either phytohaemagglutin or 17 -oestradiol or both, and the enzyme activities of nicotinamide adenine dinucleotide phosphate-linked glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase were assayed. As a result, it was found that these enzymes were considerably induced by oestradiol in phytohaemagglutinin-stimulated lymphocytes, but not in non-stimulated cells. Electrophoretic studies on glucose-6-phosphate dehydrogenase showed that six molecular forms are demonstrable in normal and phytohaemagglutinin-stimulated leucocytes, and that one of the forms was specifically induced by oestradiol in the presence of phytohaemagglutinin.     

The post-mortem stability of certain oxidative enzymes in brain and spinal cord

Summary An investigation has been carried out on the stability of several enzymes in portions of rabbit brain and spinal cord kept at controlled temperatures between 22 and 37° C for periods up to 24 hours before processing for enzyme activity. The enzymes studied were NAD diaphorase, succinate, lactate, glutamate and glucose-6-phosphate dehydrogenases, and monoamine oxidase. One-wavelength plug cytophotometric measurements of enzyme activity were carried out on Purkinje cells, neuropil of the granular layer of the cerebellar cortex and on anterior horn cells.Succinate dehydrogenase activity proved to be stable after 24 hours post-mortem exposure at 37°C. Lactate dehydrogenase, NAD diaphorase and monoamine oxidase activities were less stable at the higher temperatures but were stable at 22°C. Glutamate and glucose-6-phosphate dehydrogenase activities fell significantly with exposure at 22°C. It thus appears possible to make valid histochemical measurements of the activities of certain oxidative enzymes in selected post-mortem brain material.This research was aided by a grant from the National Health and Medical Research Council of Australia.     

An automatic enzymatic determination of glycogen in a continuous-flow system without interference of free glucose.

An autoanalyzer system for enzymatic determination of glycogen is described. Free glucose is eliminated by hexokinase/glucose-6-phosphate dehydrogenase. Glycogen is hydrolyzed by amylo-1,6-glycosidase at pH 4,8, and the resulting glucose is dialyzed and determined by the hexokinase/glucose-6-phosphate dehydrogenase reaction.     

Activity of some enzymes in Physarum polycephalum

Summary The activities of seven enzymes were studied during the first 24 h of spherule formation (differentiation) in cultures of Physarum polycephalum. These enzymes were: isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, acid phosphatase, phosphodiesterase, -glucosidase, and histidase. Isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase showed a decrease, glutamate dehydrogenase and phosphodiesterase increased about eight-fold, acid phosphatase about two-fold, -glucosidase showed an activity peak at about 15 h after starvation which decreased, after 24 h to its original value, and histidase showed no significant activity change during the period. The inhibition of protein synthesis by cycloheximide resulted in a decrease of enzymic activity at all times during the process, whereas the inhibition of RNA synthesis by actinomycin D had no effect during the early stages of spherulation but resulted in a rather rapid decrease of enzymic activity when added 21 h after the initiation of spherule formation. Attempts to induce higher enzymic activities during spherulation above the levels already observed were unsuccessful.

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Zusammenfassung Der Aktivitätsverlauf, von sieben Enzymen wurde während der ersten 24 Std der Mikrosklerotienbildung verfolgt. Es handelte sich um die Enzyme: Isocitratdehydrogenase, Glucose-6-Phosphat Dehydrogenase, Glutamat-dehydrogenase, saure Phosphatase, Phosphodiesterase, -Glucosidase und Histidase. Isocitratdehydrogenase und Glucose-6-Phosphat Dehydrogenase nahmen während dieser Zeit ab, Glutamatdehydrogenase und Phosphodiesterase stiegen auf das 8fache des Ausgangswertes, saure Phosphatase auf das 2fache. -Glucosidase zeigte ein Aktivitätsmaximum nach ungefähr 15 Std, das aber nach etwa 24 Std wieder bis zu dem Ausgangswert abnahm, während Histidase sich nicht signifikant veränderte. Die Hemmung der Proteinsynthese durch Cycloheximid resultierte zu jedem Zeitpunkt in einer sofortigen Abnahme der Enzymaktivität, während die Inhibition der RNS-Synthese in der ersten Zeit ohne Effekt war, jedoch bei einer Zugabe nach 21 Std nach der Induktion der Spherulation eine ziemlich schnelle Abnahme der Enzymaktivität bewirkte. Versuche, die Enzymaktivitäten zusätzlich zu den schon beobachteten zu induzieren, schlugen fehl.

     

Enzyme activity profiles in an overwintering population of freeze-tolerant larvae of the gall fly,Eurosta solidaginis

The activity of some enzymes of intermediary metabolism, including enzymes of glycolysis, the hexose monophosphate shunt, and polyol cryoprotectant synthesis, were measured in freeze-tolerant Eurosta solidaginis larvae over a winter season and upon entry into pupation. Flexible metabolic rearrangement was observed concurrently with acclimatization and development. Profiles of enzyme activities related to the metabolism of the cryoprotectant glycerol indicated that fall biosynthesis may occur from two possible pathways: 1. glyceraldehyde-phosphate glyceraldehyde glycerol, using glyceraldehyde phosphatase and NADPH-linked polyol dehydrogenase, or 2. dihydroxyacetonephosphate glycerol-3-phosphate glycerol, using glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase. Clearance of glycerol in the spring appeared to occur by a novel route through the action of polyol dehydrogenase and glyceraldehyde kinase. Profiles of enzyme activities associated with sorbitol metabolism suggested that this polyol cryoprotectant was synthesized from glucose-6-phosphate through the action of glucose-6-phosphatase and NADPH-linked polyol dehydrogenase. Removal of sorbitol in the spring appeared to occur through the action of sorbitol dehydrogenase and hexokinase. Glycogen phosphorylase activation ensured the required flow of carbon into the synthesis of both glycerol and sorbitol. Little change was seen in the activity of glycolytic or hexose monophosphate shunt enzymes over the winter. Increased activity of the -glycerophosphate shuttle in the spring, indicated by greatly increased glycerol-3-phosphate dehydrogenase activity, may be key to removal and oxidation of reducing equivalents generated from polyol cryoprotectan catabolism.Abbreviations 6PGDH 6-Phosphogluconate dehydrogenase - DHAP dihydroxy acetone phosphate - F6P fructose-6-phosphate - F6Pase fructose-6-phospha-tase - FBPase fructose-bisphosphatase - G3P glycerol-3-phosphate - G3Pase glycerol-3-phosphate phophatase - G3PDH glycerol-3-phosphate dehydrogenase - G6P glucose-6-phosphate - G6Pase glucose-6-phosphatase - G6PDH glucose-6-phosphate dehydrogenase - GAK glyceraldehyde kinase - GAP glyceraldehyde-3-phosphate - GAPase glyceraldehyde-3-phosphatase - GAPDH glyceraldehyde-3-phosphate dehydrogenase - GDH glycerol dehydrogenase - GPase glycogen phosphorylase - HMS hexose monophosphate shunt - LDH lactate dehydrogenase - NADP-IDH NADP⁺-dependent isocitrate dehydrogenase - PDHald polyol dehydrogenase, glyceraldehyde activity - PDHgluc polyol dehydrogenase, glucose activity - PFK phosphofructokinase - PGI phosphoglucoisomerase - PGK phosphoglycerate kinase - PGM phosphoglucomutase - PK pyruvate kinase - PMSF phenylmethylsulfonylfluoride - SoDH sorbitol dehydrogenase - V _max maximal enzyme activity - ww wet weight