Behavior of transaldolase (EC 2.2.1.2) and transketolase (EC 2.2.1.1) Activities in normal, neoplastic, differentiating, and regenerating liver.

摘要: The objective of this investigation was to throw light on the biological behavior and metabolic regulation hepatic enzymes nonoxidative branch pentose phosphate pathway. activities transaldolase (EC 2.2.1.2) transketolase 2.2.1.1) were compared in conditions that involve modulation gene expression such as starvation, differentiation, after partial hepatectomy, a spectrum hepatomas different growth rates. enzyme determined under optimal kinetic by spectrophotometric methods 100,000 × g supernatant fluids prepared from tissue homogenates. The properties similar normal liver rapidly growing hepatoma 3924A. For transaldolase, apparent Km values 0.13 mm (normal liver) 0.17 (hepatoma) observed for erythrose 4-phosphate 0.30 0.35 fructose 6-phosphate. pH optima at approximately 6.9 7.2. substrates, ribose 5-phosphate xylulose 5-phosphate, 0.3 0.5 mm, respectively, both hepatoma. A broad optimum around 7.6 tissues. In organ distribution studies, measured liver, intestinal mucosa, thymus, kidney, spleen, brain, adipose tissue, lung, heart, skeletal muscle. Taking specific activity 100%, highest mucosa (316%) thymus (219%); it lowest heart (53%) muscle (21%). Transketolase kidney (155%) (26%) (23%). Starvation decreased 6 days 69 74%, those normal, fed rat. This same range decrease protein concentration (66%). In tumors, increased 1.5- 3.4-fold over control rat liver. showed no relationship tumor proliferation rate. In regenerating 24 hr pathway sham-operated controls. In differentiation postnatal age 5, 12, 23, 32 days, 33, 44, 55, 72%, 60-day-old, adult male During period, 18, 21, 26, 55% rat. The demonstration hepatomas, irrespective degree malignancy, or rate, suggests reprogramming malignant transformation is linked with an increase enzyme. Since alteration found differentiating appears be neoplastic transformation. conjunction earlier glucose-6-phosphate dehydrogenase should provide selective advantages cells.