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Use of intact erythrocytes in the diagnosis of inherited purine and pyrimidine disorders
Author(s) -
Fairbanks L. D.,
Simmonds H. A.,
Webster D. R.
Publication year - 1987
Publication title -
journal of inherited metabolic disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 102
eISSN - 1573-2665
pISSN - 0141-8955
DOI - 10.1007/bf01800045
Subject(s) - hypoxanthine guanine phosphoribosyltransferase , phosphoribosyltransferase , adenine phosphoribosyltransferase , purine , purine nucleoside phosphorylase , biochemistry , adenosine deaminase , biology , enzyme , hypoxanthine phosphoribosyltransferase , nucleotide salvage , lesch–nyhan syndrome , pyrimidine metabolism , red blood cell , microbiology and biotechnology , chemistry , nucleotide , gene , mutant
This paper reports the detection of five inherited disorders of purine and one of pyrimidine metabolism using intact red blood cells (RBCs) and compares the findings with those from RBC lysate activity. Two different phosphate levels (1 and 18 mmol L −1 P i ) were used to evaluate endogenous PP‐ribose‐P levels and their generation by PP‐ribose‐P synthetase. The importance of this dual approach is demonstrated by the following evidence: Six out of eight patients with no detectable hypoxanthine‐guanine phosphoribosyltransferase (HGPRT) RBC lysate activity had up to 25% of normal activity in their intact RBCs. Two Lesch‐Nyhan patients showed no detectable activity in intact or lysed RBCs. RBC lysates from two heterozygotes for adenosine deaminase (ADA) deficiency also showed no detectable activity, but up to 60% of normal activity using intact RBCs. The existence of an aberrant enzyme in a kindred with a superactive PP‐ribose‐P synthetase was evident from the fact that intact RBCs failed to respond normally to phosphate activation, despite normal HGPRT and adenine phosphoribosyltransferase (APRT) RBC lysate activity. Raised endogenous PP‐ribose‐P levels in intact RBCs were demonstrable only in purine nucleoside phosphorylase (PNP) and HGPRT deficiency; levels were normal in APRT deficiency and hereditary oroticaciduria (OPRT/ODC) deficiency.The results indicate that diagnosis from RBC lysate activity alone may be misleading. Intact RBC studies clearly provide a better indication of the functional capacity of the enzyme in vivo . They also show a closer correlation with the clinical phenotype and allow further insight into the associated biochemical abnormalities in some cases.