[Biochemical pathways of carbon monoxide assimilation in the carboxydobacterium, Pseudomonas gazotropha]

The incorporation of 14CO into acid-stable assimilation products by Pseudomonas gazotrophia Z-1156 is characterized by a slow rate at the beginning, contrary to the rectilinear kinetics for incorporation of the bicarbonate 14C in the presence of 12CO. The assimilation of 14C-bicarbonate decelerates in the absence of CO. The relative content of 14C is the highest in phosphorylated compounds upon the shortest possible incubation of the cells of P. gazotropha Z-1156 (5 min) in the presence of 14CO and O2, and decreases in the process of incubation. The bulk of radioactivity is found in aspartate and glutamate. The composition of products formed upon the assimilation of 14CO and NaH14CO3 (in the presence of 12CO) during 15 min is similar. The key enzymes of the reductive pentose phosphate cycle have been found in the cell extracts of P. gazotropha A-1156. The specific activity of carboxylating enzymes of the Calvin cycle in the cell extracts increases in the course of proportional growth and sharply decreases when the growth of the culture decelerates. The activity of ribulose diphosphate carboxylase (EC. 4.1.1.39) is always by one-two orders lower than that of ribulose phosphate isomerase (EC. 5.3.1.6) and phosphoribulokinase (EC.2.7.1.19), but is similar to the activity of phosphoenolpyruvate carboxylase (EC. 4.1.1.31). The activity of phosphoenolpyruvate carboxykinase (EC. 4.1.1.32) has not been detected in the cells extracts of P. gazotropha Z-1156.