Abstract
The two somatomedins insulin-like growth factor I and II (IGF-I and II) purified from human plasma, have a high degree of sequence homology to proinsulin. Based on the known 3-dimensional structure of insulin this sequence homology has been used to predict conformational models of IGF-I and II. We therefore assumed that the insulin disulfide reducing thioredoxin system could be used as a model to study a possible way of degradation of IGF-I and II.
The experiments were performed by incubating 0.4-0.8 μM of each peptide together with thioredoxin and thioredoxinreductase in the presence of NADPH at room temperature. The reaction was terminated by addition of excess iodoacetic acid. The non-degraded material remaining after incubation, was measured with human placenta radioreceptor assay, with either insulin, IGF-I or II as labelled ligand.
The results show that both IGF-I and II were degraded by the thioredoxin system, with the same potency as insulin, which is in accordance with the predicted conformational models.
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Enberq, G., Holmgren, A. 52 EXPERIMENTAL MODEL FOR DEGRADATION OF SOMATOMEDINS. Pediatr Res 19, 612 (1985). https://doi.org/10.1203/00006450-198506000-00072
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DOI: https://doi.org/10.1203/00006450-198506000-00072