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A simplified method for estimating 5-phosphoribosyl 1-pyrophosphate in mouse liver and spleen
Abstract:
A simplified method for the estimation of 5-phosphoribosyl 1-pyrophosphate (PRPP) in mouse liver and spleen is described. The method uses the enzymic conversion of [8-14C] hypoxanthine to [8-14C] inosine 5'-monophosphate in the presence of PRPP and has the advantage over previously published methods in that the enzyme used in this assay, hypoxanthine-guanine phosphoribosyltransferase (HG-PRTase), is present in the tissue being analyzed and does not require preparation. In addition, each assay uses as its internal standard PRPP, thus overcoming the problem of the chemical instability inherent in this molecule. The two-minute heat treatment used in the method was found to destroy most interfering enzymes and resulted in average recovery of PRPP of 56% and 85% for the liver and spleen, respectively. The counts obtained in the assay were about ten-fold above background (80 c.p.m) and allowed accurate measurement of the phosphoribose sugar. The levels of PRPP (+/- standard deviation) found for liver and spleen in twelve (12) separate Balb/C male mice were 6.3 +/- 1.8 and 10.8 +/- 5.0 nmoles/g wet weight tissue, respectively, and agree with the tissue concentrations already reported for this metabolite. A further advantage of this assay is that it gives an index of the HG-PRTase activity in the tissues.
Insights
This study presents a simplified method for estimating 5-phosphoribosyl 1-pyrophosphate (PRPP) in mouse tissues. The assay offers improved accuracy and efficiency for measuring PRPP levels and hypoxanthine-guanine phosphoribosyltransferase (HG-PRTase) activity.
Area of Science:
- Biochemistry
- Metabolic Assays
- Mouse Models
Background:
- 5-phosphoribosyl 1-pyrophosphate (PRPP) is a crucial metabolite in nucleotide biosynthesis.
- Accurate quantification of PRPP is essential for understanding metabolic pathways.
- Existing methods for PRPP estimation often involve complex procedures and unstable internal standards.
Purpose of the Study:
- To develop a simplified and reliable method for quantifying PRPP in mouse liver and spleen.
- To establish an assay that utilizes endogenous enzymes and a stable internal standard.
- To provide an index of hypoxanthine-guanine phosphoribosyltransferase (HG-PRTase) activity.
Main Methods:
- Enzymic conversion of [8-14C] hypoxanthine to [8-14C] inosine 5'-monophosphate using endogenous HG-PRTase.
- Utilized PRPP as an internal standard to account for chemical instability.
- Employed a 2-minute heat treatment to eliminate interfering enzymes.
Main Results:
- Achieved average PRPP recovery of 56% (liver) and 85% (spleen).
- Assay counts were approximately tenfold above background, enabling accurate measurement.
- Determined PRPP levels in mouse liver (6.3 ± 1.8 nmol/g) and spleen (10.8 ± 5.0 nmol/g).
Conclusions:
- The developed method is a simplified, accurate, and efficient approach for PRPP estimation in mouse tissues.
- The assay provides a reliable index of HG-PRTase activity.
- This method overcomes limitations of previous PRPP quantification techniques.