{'fraction_non_alphanumeric': 0.04411095952705776, 'fraction_numerical': 0.02773988176443838, 'mean_word_length': 4.250596658711217, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A transport system for 2-keto-3-deoxy-D-gluconate uptake in Escherichia coli K12. Biochemical and physiological studies in whole cells.

We have presented kinetic evidence for the occurrence in Escherichia coli K 12 of an active transport system responsible for 2-keto-3-deoxy-d-gluconate uptake. It has been studied in constitutive strains PK4 and CAK 101 since it is completely cryptic in the wild-type strain. 
 
 
 
1 
The accumulation is temperature-dependent, coupled to electron and energy-yielding reactions, and is inhibited by thiol reagents. 
 
2 
2-Keto-3-deoxy-d-gluconate is not transported through the phospho-enolpyruvate-transferase system. 
 
3 
Entry reaction displays saturation kinetics obeying the Michaelis-Menten laws. The Km value has been found to be 0.25 ± 0.05 mM (at 30 °C and pH 7.0), by measuring initial rates of entrance as well as steady-state levels. Both the operator-constitutive PK4 strain and the regulator-constitutive CAK101 strain exhibit the same affinity but apparent V are 10 and 20 nmol × mg-1× min-1, respectively. 
 
4 
The 2-keto-3-deoxy-d-gluconate permeation system is endogenously induced in a strain lacking 2-keto-3-deoxy-d-gluconate kinase, when grown on any intermediary product of the hexuronide catabolic pathway, able to enter the cell and anterior to 2-keto-3-deoxy-d-gluconate in the sequence. We presented further evidence making it very likely that 2-keto-3-deoxy-d-gluconate itself is the true inducer. 
 
5 
The constitutive synthesis of the transport system is sensitive to the catabolite repression exerted by glucose and pyruvate. 
 
6 
By testing a wide number of sugars and derivatives as possible substrates, only d-glucuronate is a strictly competitive inhibitor (Ki= 1.5 mM). Since a specific hexuronate permease has been described elsewhere, we were led to demonstrate that d-glucuronate could be taken up through both its own specific system with high affinity and through the 2-keto-3-deoxy-d-gluconate specific system with lower affinity. 
 
7 
The exit reaction rate is first oder with respect to internal concentration, temperature-dependent (exit rate constant kex is 0.0180 min-1 at 30 °C) but is not carrier-mediated.