Concentrations of 6 other amino acids including alloisoleucine
, homocystine, cystathionine, cystine, argininosuccinate, [alpha]-aminoadipic acid, were not detectable (< 1 [micro]mol/L) in blood spot extracts.
Detection of alloisoleucine
is diagnostic for MSUD.
Leucine, isoleucine, alloisoleucine
, and hydroxyproline all have molecular weights of about 131 and are quantitated together for this reason.
Second-tier test for quantification of alloisoleucine
and branched-chain amino acids in dried blood spots to improve newborn screening for maple syrup urine disease (MSUD).
The metabolic profile may be further complicated by intermediate metabolites such as 3-and 4-hydroxyisovaleric acid (5), methylsuccinic acid (6), methylfumaric acid (7), isovalerylglucuronide (8), isovalerylglutamic acid (9), N-isovalerylalanine and N-isovalerylsarcosine (10), isovalerylcamitine (11), 3-hydroxyisoheptanioc acid (12), and alloisoleucine
Plasma alloisoleucine was slightly increased in patient 1 (although this was against a background of slight increases in other branched-chain amino acids) and within the reference interval in patient 2.
Plasma alloisoleucine, the first intermediate of the Rpathway, was also slightly increased in one patient, but this was an inconsistent finding because the concentration was within the reference interval in another patient.
Initial catabolic steps of isoleucine, the R-pathway and the origin of alloisoleucine.
15N conservation in the metabolic conversion of isoleucine to alloisoleucine in the rat.
We therefore examined the (patho)physiological significance of alloisoleucine plasma concentrations for the differential diagnosis of MSUD.
The range for reliable quantification of alloisoleucine was 0.
Sensitivity estimates were based on the relationship between the number of plasma samples with alloisoleucine concentrations beyond the cutoff value and the total number of plasma analyses.