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The activities of fructose-1,6-bisphosphatase, malate dehydrogenase and PEP carboxykinase were tested during discontinuous growth of the n-alkane-assimilating yeast Candida maltosa on glucose or ethanol. As expected, the highest activities of the enzymes were measured in the early log phase of growth on ethanol and the lowest in the early log phase of growth on glucose. However, the differences in the activities are much smaller than in Saccharomyces cerevisiae and other yeasts under similar conditions. Therefore, we conclude that catabolite repression does not play an essential role in the control of gluconeogenesis in Candida maltosa.

Transitory Lactic acidemia may be found under very different conditions, eg. hyperventilation, hypoxia, strenuous muscular work, diabetic ketoacidosis, malignancies and totally parenteral alimentation. In contrast chronic, permanent lactic acidemia and lactic aciduria may point to one of several and usually severe inherited metabolic diseases of gluconeogenesis, pyruvate oxidation, the Krebs cycle or the respiratory chain. Clinical hints for a stepwise differential diagnosis are presented.

The activity of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) was determined radiometrically in heart and skeletal muscle (M. semitendinosus) of 21 fetuses of the last third of gestation (80th-112th day), 17 piglets from birth until the 9th day of life and 7 fattening pigs. Simultaneously the activity of the enzymes glucose-6-phosphatase (G6Pase) and fructosebisphosphatase (FDPase) was measured colorimetrically in heart and skeletal muscle of piglets and in skeletal muscles of fattening pigs. Heart and skeletal muscle have only a low PEPCK activity. During the last third of gestation PEPCK in heart remains on a constant level, which can be demonstrated also in fattening pigs, but doubled immediately after birth. During the last two weeks of gestation, at birth and during the first days of life the PEPCK activity in the skeletal muscle is 3-fold higher than at the 80th day of gestation and in fattening pigs. G6Pase and FDPase activity of the heart remains at a constant level during the first days of life. It was impossible to detect G6Pase in the skeletal muscle of piglets. The specific FDPase activity of the skeletal muscle remains constant also postnatally. In fattening pigs skeletal muscles with different types of fibres have the same FDPase and PEPCK activity.

In pig fetuses (19 of 8 dams) developed by Caesarean section the dry matter and protein content of the kidneys and their PEPCK activity remain constant during the last third (from 80th to 112th day) of gestation. After birth the dry matter content of the kidneys rises slowly, but their protein content remarkably. In the kidneys of suckling piglets (17 animals of 3 offsprings) the FDPase activity remains at the same level from birth to the 9th day of life, while in the same time the G6Pase activity rises 1.5-2 times. In the kidneys of newborn piglets the total PEPCK activity increases 3-4 times and the activity of the cytosolic enzyme 2-3 times during the first 12 hours of life. At the end of the first week of life the total PEPCK activity decreases by one-third, while the activity of the cytosolic enzyme remains stable. In the kidneys of slaughter pigs (n = 7) the dry matter content and the FDPase activity are significantly higher, the protein content and the G6Pase activity are the same as in the kidneys of piglets. The total PEPCK activity is one-half, the activity of the cytosolic enzyme one-third lower than in the kidneys of piglets. In the kidneys of adult pigs the PEPCK activity is localized to equal parts in the cytosol and in the mitochondria, but in some development stages the mitochondrial part exceeds that of the cytosol. In adult pigs the PEPCK activity of the renal cortex is 2.5-3 times higher than that of the renal medulla.

The possible role of some metabolic systems producing acetyl-CoA, and methylmalonyl-CoA as initial precursors in the biosynthesis of the macrolide antibiotic A 6599 by Streptomyces hygroscopicus JA 6599 was studied. The activities of pyruvate decarboxylase exceeded in two higher producing strains about twofold those found in the mycelium of a lower producing one suggesting that in this organism an enhanced production of acetyl-CoA should be one of the prerequisites necessary for an improved antibiotic biosynthesis. No clear interrelationship was established, however, between the biosynthesis of the secondary metabolite A 6599 on the one hand and the acetate and propionate kinase content on the other hand. In S. hygroscopicus JA 6599 the carboxylation of acetyl-CoA or propionyl-CoA seems to be the major pathway giving malonyl-CoA or methylmalonyl-CoA, respectively. Thus, the activities of acetyl-CoA and propionyl-CoA carboxylases corresponded with both the levels of antibiotic production in several strains and with variations observed in the specific antibiotic production rate during the cultivation. Some other pathways synthesizing these precursors, e.g. via oxaloacetate, are assumed to be negligible since even in the mycelium of the lower producing strain increased activities of phosphoenolpyruvate carboxylase were present.

Described in this paper is a technique for the determination of pyruvate carboxylase and phosphoenolpyruvate carboxykinase, two key enzymes of gluconeogenesis in swine liver. The technique is based on measurement of radioactively labelled carbon incorporated in the common metabolite, oxalacetate. The optimum measuring conditions to establish the enzymes in liver homogenate and supernatant are reported and compared with data given by other authors. The found parameters of kinetic properties were in good agreement with the findings obtained from purified enzymes from swine liver.

The excessive production of pyruvic and 2-oxoglutaric acid by S. hygroscopicus JA 6599 grown on a medium rich in complex carbon and nitrogen sources was studied. Towards the end of the first day of batch cultivation a maximum level of both keto acids in the medium was observed. By diluting the complete culture with water at 22nd hour, however, a further increase in 2-oxoglutarate concentration was induced and the antibiotic production was slightly stimulated. In diluted cultures the oxygen saturation was found to be distinctly higher than in non-diluted ones and, on the other hand, the mycelial activities of both pyruvate and 2-oxoglutarate decarboxylases were decreased. Since the 2-oxoglutarate level was strongly influenced by inhibitors of glycolysis and of citric acid cycle, it is suggested that the metabolite accumulation in diluted cultures is mainly caused by modifications of the metabolic control of carbohydrate catabolism due to an improved aeration. Furthermore, the macrolide antibiotic A 6599 produced by S. hygroscopicus JA 6599 itself was shown to interfere with the accumulation of 2-oxoglutaric acid.

Low-protein (5%) and high-protein (40%) diets as well as low-fat (5%) and high-fat (40%) diets were fed to weanling rats in a 14-day experiment, the standard diet containing 10% of protein and 10% of fat. The net protein utilization of casein, the liver protein utilization and the activity of the key enzyme of gluconeogenesis in the liver, phosphoenol pyruvate carboxykinase, were determined. The utilization of proteins by the organism was adversely affected by a high intake of proteins and also of fats. This fact and the observed stimulation of gluconeogenesis testify to the physiological and economical unsuitableness of diets containing excessive amounts of proteins and fats. A low fat intake was less detrimental to the utilization of proteins than a high fat intake; a low intake of proteins seemed to improve the utilization, but other parameters evidenced that it is not sufficient. The application of diets with closely graded contents in wide ranges for various times will yield biochemical indicators being of importance as supplementary factors in the determination of the physiological value of nutrients under different conditions.

Using a radiochemical method the activity of the gluconeogenic key enzymes phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) was determined in liver homogenates of 58 piglets (from birth to 10 days of life), 4 weaners and 18 fattening pigs. Simultaneously, the cytosolic PEPCK activity was estimated. In liver of newborn piglets (immediately after birth without suckling) total PEPCK activity is one half, cytosolic PEPCK activity one sixth and PC activity one half of that occurring in adult pig's liver. During regular suckling within the first 12 h of life, the total PEPCK activity of piglet liver rises slowly, however, cytosolic PEPCK activity increases 3 to 4 times and PC activity in the mitochondria twice. After the 2nd day of life the activity of both enzymes reaches a level which is kept during the whole suckling period: total PEPCK activity is 1.5 to 2-fold, cytosolic PEPCK activity is 2 to 3-fold higher, and PC activity is at the level existing at birth. In weaners cytosolic PEPCK activity further rises to the level existing in the liver of adult pigs. The PEPCK and PC activities in the liver at birth enables the piglet for gluconeogenesis, but due to the postnatal increase of enzyme activities, the prerequisites for an intensive synthesis of glucose are given only after the 2nd day of life.

The gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) and the glycolytic enzyme pyruvate kinase (PK), regulating pyruvate metabolism, were determined in the livers of 71 fetuses, which were developed of 25 dams on the 80th, 100th, 106th, and 112th day of gestation (length: 115 days) by Caesarean section. For comparative purposes the same enzymes were estimated in 12 naturally born piglets immediately after delivery. During the period under examination (the last third of gestation) the total activity of PEPCK has its highest values at the 80th day, the PC and PK activity at the 100th day of gestation. The activities of all 3 enzymes decrease during the last 2 weeks of gestation until birth. The cytosolic part of PEPCK amounts to 10-15 per cent of total activity and develops in a parallel manner. In newborn piglets a further decline of the PC and total PEPCK activity can be observed, but the cytosolic PEPCK activity remains constant, and therefore its relative proportion increases to 25% of the total activity. The PK activity rises distinctly (1.5 times). The role of these enzymes in the carbohydrate metabolism of the fetus, especially in gluconeogenesis, is discussed in detail.

Several biophysical and biochemical changes are prerequisites for the adaptation of the newborn to extrauterine life. Enzyme induction is the mechanism on which this adaptation of metabolism is based. The theoretical fundamentals of enzyme induction are presented, and the perinatal origin of enzymes explained by means of the example of PEP carboxykinase. Among the mose frequent disturbances of the maturing of organs are hyperbilirubinaemias and the respiratory distress syndrome of newborn. The biochemical and physical concepts underlying these disease pattens are explained, and possibilities of enzyme induction and hence acceleration of maturity are shown. On the grounds of clinical experience, enzyme induction appears to be safely established as a membrane prophylaxis.

Phosphoenolpyruvate carboxykinase (PEPCK) from Phycomyces blakesleeanus was partially purified by protamine sulfate precipitation, ammoniumsulfate precipitation, and diethylamino ethyl cellulose (DEAE) treatment. This preparation was employed for the characterization of the enzyme. The Km values for phosphoenolpyruvate (PEP) and ADP were determined as 1.6 and 0.42 mM. The nucleotid specificity was demonstrated for ADP exclusively. The use of sulfuryl reagents showed the presence of thiol groups sensitive against p-hydroxymercuribenzoate but not effected by N-ethylmaleimide.