The influence of pH and urine composition on urease enzymatic activity in human urine

Abstract

It is reasonable to assume that the rate of pH increase in urine induced by urease-producing microorganisms is one of the factors which determine whether crystallisation with subsequent stone formation will occur or not. To evaluate how the time needed to increase urine pH varies between different urine samples and how it depends on urine composition, a standardised amount of urease was added to different human urine samples. The incubations were performed in a pH-stat. This allowed simultaneous study of how urease enzymatic activity depends on urine pH and how it varies between different urines. The enzymatic activity was found to be negatively correlated to urine pH and to vary between different urines. The rate of the pH increase varied markedly between different urines. Small pH increases depended on the native urine pH and urease enzymatic activity. Higher pH increases up to the levels of phosphate crystallisation depended more on urine phosphate, the major urine buffer. The results presented show that urine composition influences the urease-induced pH increase. This might have clinical implications.

The influence of thermal reaction and microbial transformation on the odour of human urine

“…[63] When urine is excreted, the major proportion of the nitrogen is present as urea (constituting about 2% of human urine); during bacterial fermentation, this is converted to 2NH 4 + and CO 3 2À . Edin-Liljegren et al [18] have shown that urease activity was highest at pH 6.4. We confirmed the previous observation that, in pure urine samples, no Enterobacteriaceae survived after 3 days at 37 C. [60] Faecal streptococci (Enterococci) are considered more resistant than Enterobacteriaceae at a higher pH and nitrogen content.…”

“…When urine is excreted, the major proportion of the nitrogen is present as urea (constituting about 2% of human urine); during bacterial fermentation, this is converted to 2NH 4 + and CO 3 2− . Edin‐Liljegren et al . have shown that urease activity was highest at pH 6.4.…”

“…In the literature, the link between bacterial β ‐glucuronidases and tryptophanases and the generation of odorant compounds is widely reported . In addition, urease‐positive bacteria such as Staphylococcus intermedius , P. vulgaris , Klebsiella and Bacteroides ureolyticus are known to metabolize urea to ammonia . However, the link to malodour generation in healthy individuals has not been made, probably because the majority of authors have historically focused on UTI and its treatment, and only a limited amount of analytical work has been carried out on urine volatiles per se .…”

Synthesis of Calcium Carbonate Crystals by Using Bacteria

“…[22] The common bacteria, Escherichia coliform (E. coli), were found in urinary stones and they could damage the protective antiadhesive GAG layer and cause crystal retention or they could alter urine composition in a way that favored stone formation. [23] However, there is rare report about their true role in biomineralization process of urinary stones. In this study, we found that the E. coli could induce the nucleation, growth, and aggregation of CaCO 3 by bacterial biomolecules and make the particles become larger.…”

The Role of Escherichia coliform in the Biomineralization of Calcium Oxalate Crystals

“…The common bacterium Escherichia coliform ( E. coli ) is often found in urinary stones and it could damage the protective anti‐adhesive GAG layer and cause crystal retention or alter urine composition in such a way that favors stone formation 26,27. It has also been found that E. coli plays an important role in urinary‐tract infections 28.…”