Mutant urease and method of use for determination of urea
AssigneeBoard of Trustees operating Michigan State University
InventorRobert P. Hausinger
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Abstract
A mutant urease of Klebsiella aerogenes characterized as .alpha.H219Q having a glutamine (Q) in position 219 in place of histidine (H). The resulting enzyme has a low affinity for substrate (high value of K.sub.m) and is particularly useful in assays and test kits for measuring urea concentrations in body fluids.
Claims4
A urease of Klebsiella aerogenes having a modified urease .alpha. subunit, designated as .alpha.H219Q, having glutamine as substituent number 219 of the .alpha. subunit as set forth in SEQ ID NO:
- 5 and having an optimum pH of 6.2 with a rate with urea as a substrate that is about 45% of that of the urease of the Klebsiella aerogenes.
In a method for converting urea to carbonic acid and ammonia with an enzyme, the improvement which comprises using the .alpha.H219Q variant of urease of Klebsiella aerogenes having a modified .alpha. subunit, designated as H219Q, having glutamine as substituent 219 of the .alpha. subunit for the conversion as set forth in SEQ ID NO:
- 5, wherein the urease has a low affinity for urea and thus a higher K.sub.m as compared to .alpha.H219 and having an optimum pH of 6.2 with a rate with urea as a substrate that is about 45% of that of the urease of the Klebsiella aerogenes.
In a method for assaying for urea in a body fluid by conversion of the urea to carbonic acid and ammonia as products with a urease and detecting the products, the improvement which comprises using a urease of Klebsiella aerogenes having a modified .alpha. subunit, designated as H219Q, having glutamine as substituent 219 of the .alpha. subunit as set forth in SEQ ID NO:
- 5 for the conversion to the products in the assay which are then detected, wherein the urease has a low affinity for the urea and thus a higher K.sub.m as compared to .alpha.H219 and having an optimum pH of 6.2 with a rate with urea as a substrate that is about 45% of that of the urease of the Klebsiella aerogenes.
In a test kit for assaying for urea in a body fluid by conversion of urea to carbonic acid and ammonia as products with an enzyme including a means for detecting one or more of the products of the urea, the improvement which comprises:
- providing in the kit a urease of Klebsiella aerogenes having glutamine as substituent 219 of the .alpha. subunit as set forth in SEQ ID NO:
- 5 and having an optimum pH of 6.2 with a rate with urea as a substrate that is about 45% of that of the urease of the Klebsiella aerogenes for use to make the conversion.
Dependencies are inferred from the claim text.