Unstable argininosuccinate lyase in variant forms of the urea cycle disorder argininosuccinic aciduria.

Hu, Liyan; Pandey, Amit Vikram; Balmer, Cécile; Eggimann, Sandra; Rüfenacht, Véronique; Nuoffer, Jean-Marc; Häberle, Johannes (2015). Unstable argininosuccinate lyase in variant forms of the urea cycle disorder argininosuccinic aciduria. Journal of inherited metabolic disease, 38(5), pp. 815-827. Springer 10.1007/s10545-014-9807-3

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Loss of function of the urea cycle enzyme argininosuccinate lyase (ASL) is caused by mutations in the ASL gene leading to ASL deficiency (ASLD). ASLD has a broad clinical spectrum ranging from life-threatening severe neonatal to asymptomatic forms. Different levels of residual ASL activity probably contribute to the phenotypic variability but reliable expression systems allowing clinically useful conclusions are not yet available. In order to define the molecular characteristics underlying the phenotypic variability, we investigated all ASL mutations that were hitherto identified in patients with late onset or mild clinical and biochemical courses by ASL expression in human embryonic kidney 293 T cells. We found residual activities >3 % of ASL wild type (WT) in nine of 11 ASL mutations. Six ASL mutations (p.Arg95Cys, p.Ile100Thr, p.Val178Met, p.Glu189Gly, p.Val335Leu, and p.Arg379Cys) with residual activities ≥16 % of ASL WT showed no significant or less than twofold reduced Km values, but displayed thermal instability. Computational structural analysis supported the biochemical findings by revealing multiple effects including protein instability, disruption of ionic interactions and hydrogen bonds between residues in the monomeric form of the protein, and disruption of contacts between adjacent monomeric units in the ASL tetramer. These findings suggest that the clinical and biochemical course in variant forms of ASLD is associated with relevant residual levels of ASL activity as well as instability of mutant ASL proteins. Since about 30 % of known ASLD genotypes are affected by mutations studied here, ASLD should be considered as a candidate for chaperone treatment to improve mutant protein stability.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Institute of Clinical Chemistry
04 Faculty of Medicine > Department of Gynaecology, Paediatrics and Endocrinology (DFKE) > Clinic of Paediatric Medicine > Endocrinology/Metabolic Disorders

UniBE Contributor:

Pandey, Amit Vikram, Nuoffer, Jean-Marc


600 Technology > 610 Medicine & health
500 Science > 570 Life sciences; biology






[4] Swiss National Science Foundation


[102] Pathogenesis of disorders caused by human P450 oxidoreductase mutations Official URL




Amit Vikram Pandey

Date Deposited:

05 May 2015 14:48

Last Modified:

06 Jan 2023 19:04

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