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Ribose-5-phosphate isomerase deficiency (RPID) is a rare human disorder caused by mutations in ribose-5-phosphate isomerase, an enzyme of the pentose phosphate pathway.With only four known cases – all diagnosed between 1984 and 2019 – RPI deficiency is the second rarest disease, with Fields condition being the rarest, affecting two known individuals, Catherine and Kirstie Fields.
Ribose-5-phosphate isomerase (Rpi) encoded by the RPIA gene is an enzyme (EC 5.3.1.6) that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). It is a member of a larger class of isomerases which catalyze the interconversion of chemical isomers (in this case structural isomers of pentose ).
Ribose 5-phosphate (R5P) is both a product and an intermediate of the pentose phosphate pathway. The last step of the oxidative reactions in the pentose phosphate pathway is the production of ribulose 5-phosphate. Depending on the body's state, ribulose 5-phosphate can reversibly isomerize to ribose 5-phosphate.
It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. [1] While the pentose phosphate pathway does involve oxidation of glucose, its primary role is anabolic rather than catabolic. The pathway is especially important in red blood cells (erythrocytes).
The precursor 45S rDNA is organized into 5 clusters (each has 30-40 repeats) on chromosomes 13, 14, 15, 21, and 22. These are transcribed in the nucleolus by RNA polymerase I . 45S is processed in the nucleus via 32S rRNA to 28S [ 6 ] and 5.8S , [ 7 ] and via 30S to 18S , [ 8 ] as shown in the diagram. 18S is a component of the ribosomal 40S ...
In enzymology, a ribose isomerase (EC 5.3.1.20) is an enzyme that catalyzes the chemical reaction D-ribose ⇌ {\displaystyle \rightleftharpoons } D-ribulose Hence, this enzyme has one substrate , D-ribose , and one product , D-ribulose .
Phosphohexose Isomerase Deficiency (PHI) is also known as phosphoglucose isomerase deficiency or Glucose-6-phosphate isomerase deficiency, and is a hereditary enzyme deficiency. PHI is the second most frequent erthoenzyopathy in glycolysis besides pyruvate kinase deficiency , and is associated with non-spherocytic haemolytic anaemia of variable ...
Glucose-6-phosphate isomerase deficiency affects step 2 of glycolysis. Triosephosphate isomerase deficiency affects step 5 of glycolysis. Phosphoglycerate kinase deficiency affects step 7 of glycolysis. Pyruvate kinase deficiency affects the 10th and last step of glycolysis. [citation needed]