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Serum levels of Lactate Dehydrogenase (LDH), alpha-Hydroxybutyrate Dehydrogenase (HBDH) and the relative ratio of alpha-Hydroxybutyrate Dehydrogenase to Lactate Dehydrogenase (HBDH/LDH) were determined in 51 cases of histologically proved testicular germ cell tumors and 40 healthy controls. Serum LDH and HBDH levels were found to be raised in both seminomatous and non-seminomatous germ cell tumors. The ratio of HBDH/LDH was found to be statistically significant in seminomas and insignificant in non-seminomatous germ cell tumors. Furthermore, the levels of LDH and HBDH showed a fall, following treatment indicating response to therapy. Serum LDH and HBDH could both be used as tumor markers in the diagnosis of testicular germ cell tumors as well as prognostic indicators in monitoring therapy, HBDH, being more specific in monitoring therapy as compared to serum LDH.
The total activities of lactate dehydrogenase (LD) and hydroxybutyrate dehydrogenase (HBD), and the LD isoenzyme distribution were determined in tissue samples taken in vivo from different parts of the rabbit brain, and in cortical grey, subcortical white, and cerebellar tissue from man. The total LD and HBD activities were found to be higher in the brain stem than in the cerebral hemisphere, basal ganglia, and cerebellum of the rabbit brain. The isoenzyme distribution in the brain stem and the cerebellum showed an anodal shift, i.e., significantly higher activities of LD1 compared with the cerebral hemisphere and the basal ganglia. In man the total LD activity was found to be lower in white than in grey matter, although the isoenzyme patterns did not differ. The implications of these findings in relation to the LD isoenzyme pattern in serum after traumatic brain injury are discussed.
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The activity of delta5-3beta Hydroxysteroid hydro-genase, dihydro orotic dehydrogenase, B-Hydroxybutyrate dehydrogenase and glucose-6-phosphate dehydrogenase was studied in the testes of hereditary dwarf mice treated with Prolactin or LH. Two months old dw/dw dwarf mice were injected twice daily, for 14 days, either with 100 mug ovine Prolactin, or 5 mug ovine LH twice a day. Prolactin treatment increased the activity of all the enzymes assessed. Treatment with LH stimulated the activity of all the enzymes as compared to the saline treated animals but less than the Prolactin treated ones. The data bearing that the increased activity of several oxidising enzymes in the testes of hereditary dwarf mice is increased with Prolactin, is consistent with the suggested effect of this hormone on testicular steroidogenesis.
The postnatal maturation of glucose-6-phosphate and beta-hydroxybutyrate dehydrogenase activity was assessed by histochemistry in rats at eight postnatal stages, P0, P5, P10, P14, P17, P21, P35 and the adult stage. Enzyme activities were revealed on cryostat brain sections with nitroblue tetrazolium. Both enzyme activities were low and homogeneous at birth, and increased to reach a peak in all areas studied, at P17 for beta-hydroxybutyrate dehydrogenase and at P21 for glucose-6-phosphate dehydrogenase. Then, glucose-6-phosphate dehydrogenase activity decreased regularly by 20-49% from P21 to adult stage, except in cerebellar white matter where activity did not change after P21. beta-hydroxybutyrate dehydrogenase activity decreased regularly from P17 to adult stage in globus pallidus, hippocampus, thalamus, brainstem, genu of corpus callosum and cerebellar white matter. It sensorimotor cortex, medial geniculate body, caudate nucleus, hypothalamus and inferior colliculus, beta-hydroxybutyrate dehydrogenase activity stayed stable between P17 and P35 and decreased thereafter to adult levels. Finally, in parietal, auditory and cerebellar cortices, beta-hydroxybutyrate dehydrogenase activity either stayed stable or slightly increased after P17. The present study shows that there is a quite good correlation between postnatal changes in cerebral glucose-6-phosphate and beta-hydroxybutyrate dehydrogenase activities and the importance of pentose phosphate pathway and ketone body utilization in the developing brain. Our results also reflect the regional heterogeneity of beta-hydroxybutyrate utilization in the adult rat brain, translating into a remaining high activity of beta-hydroxybutyrate dehydrogenase in cerebral cortex.
In a study on enzyme activities in normal human myocardial tissue the activities of lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (HBDH), creatine kinase (CK), and aspartate aminotransferase (AST), and the activities of the isoenzymes of LDH (1--5) and AST (c and m) were measured in myocardial specimens obtained from live patients (18 biopsies) and postmortem (14 autopsies). Comparison of measurements in 4 right ventricular biopsies from 1 patient with those in 9 right ventricular biopsies from 9 patients shows that (1) the enzymes studied are homogeneously distributed throughout the right ventricular myocardium, (2) errors in the measurement of the activities of the enzymes studied are within 5%, and (3) inter-individual differences in myocardial enzyme activities are quite considerable (10--17%). No significant differences in the activities of the enzymes studied were found between left and right ventricular myocardium. The effect of autolysis on the activities of the enzymes studied in myocardial specimens obtained postmortem is small, amounting to -1% to -6% in the first 10 h, irrespective of whether a linear or an exponential decay of enzyme activity is assumed. Comparison of myocardial enzyme activities in biopsies with those in autopsies, the latter being corrected for autolysis-induced inactivation, reveals significant differences with respect to CK, AST and mAST. At present it is impossible to conclude whether these differences were due to the different conditions existing before the myocardial specimens were frozen at -20 degrees C or to the different types of pathology present in the hearts from which the specimens were taken.
Four cytoplasmically synthesized rat liver mitochondrial enzymes, located either as soluble enzymes in the mitochondrial matrix (L-glutamate dehydrogenase and malate dehydrogenase or in the intermembrane space (sulfite oxidase) or as an integral membrane protein located on the matrix face of the inner mitochondrial membrane (D-beta-hydroxybutyrate dehydrogenase), were all shown to be synthesized as precursors larger than their mature counterparts by 1000-6000 daltons. These larger forms were detected in vitro, in a cell-free protein synthesizing system programmed with either total rat liver RNA or with RNA isolated from free polysomes or with free polysomes, and in vivo, in the two cases that were investigated (L-glutamate dehydrogenase and D-beta-hydroxybutyrate dehydrogenase), by pulse labeling of Buffalo rat liver cells in culture. The intracellular site of synthesis of all four mitochondrial enzymes was shown to be primarily on free polysomes and not on membrane-bound polysomes.
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The effects of methylmalonate (MMA) on succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase (HBDH) activities in brain and liver of 15-day-old rats were studied. The apparent Km of SDH for succinate was 0.45 mmol/L in brain and 0.34 mmol/L in liver. MMA inhibited the enzyme activity in both tissues with Ki values of 4.5 mmol/L and 2.3 mmol/L in brain and liver, respectively, and the inhibition was of the reversible competitive type. The calculated Km for HBDH with beta-hydroxybutyrate as substrate was 1.26 mmol/L in brain and 0.36 mmol/L in liver. MMA inhibited the enzyme with a Ki value of 0.015 mmol/L in brain and 0.275 mmol/L in liver. These results are probably relevant to our understanding of cerebral metabolism in methylmalonic acidaemic children, especially during ketoacidotic and hypoglycaemic crises, and may be related to the pathogenesis of cerebral dysfunction of methylmalonic acidaemia.
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2,3-Epoxybutyrate and 2,3-epoxypropionate act as effective competitive inhibitors of pig heart lactic dehydrogenase. KIapp for both inhibitors was pH dependent and varied according to the general equation KIapp = KI(1 +Ka/H+) which may be predicted if the binding of the epoxide to the E-NADH complex involves a compulsory protonation step. Values of KI(epoxybutyrate), KI(epoxypropionate) and pKa were estimated as 150 muM, 860 muM, and 6.8, respectively. The formation of an E-NADH epoxide inhibitor complex was followed directly by fluorescence measurements. Both epoxybutyrate and epoxypropionate enhanced fluorescence of the E-NADH complex and caused a 20-nm blue shift in the maximum emission wavelenght. The dissociation constants measured by fluorescence titration for both epoxides increased as the pH was raised reflecting a decreased affinity for the E-NADH complex. 2,3-Epoxybutyrate was also shown to inhibit beta-hydroxybutyrate dehydrogenase by a mechanism which is consistent with compulsory protonation prior to addition of the epoxide. These results are discussed in terms of a general mechanism for the bond forming events in pyridine nucleotide linked oxidore-ductases.
Two D-(-)-3-hydroxybutyrate (3HB) dehydrogenases, BDH1 and BDH2, were isolated and purified from a poly(3-hydroxybutyrate) (PHB)-degradable bacterium, Ralstonia pickettii T1. BDH1 activity increased in R. pickettii T1 cells grown on several organic acids as a carbon source but not on 3HB, whereas BDH2 activity markedly increased in the same cells grown on 3HB or PHB. To examine their biochemical properties, bdh1 and bdh2 were cloned and overexpressed in Escherichia coli, and their purified products were characterized. The kinetic parameters indicate that BDH1 is more suitable for converting acetoacetate to 3HB than BDH2, whereas BDH2 is more efficient for the reverse reaction than BDH1. Thus, R. pickettii T1 contains two BDHs with different biochemical properties and physiological roles: BDH1 for cell growth on organic acids other than 3HB and BDH2 for cell growth on 3HB or PHB.
beta-Hydroxybutyrate dehydrogenase (EC 1.1.1.30.)-an enzyme involved in degradation of polymer store material-was found in staphylococci. The enzyme was isolated from Staphylococcus xylosus NCTC D100694 cells, purified and characterized. The native enzyme is a tetramer and consists of equal subunits. Its relative molecular mass is M(r) = 140 kDa and pI = 4.7. The enzyme activity is stimulated by Mg+2 and Ca+2 ions. Staphylococcal beta-hydroxybutyrate dehydrogenase is relatively stable and active in a wide temperature range. The optimum pH for oxidation is 8.6 and for reduction 6.7. The enzyme is highly specific for D(-)stereoisomer of beta-hydroxybutyrate. Km values for beta-hydroxybutyrate and acetoacetate are 39.1 microM and 5.47 microM, respectively.
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