Flow injection method for the determination of thyroxine by inhibition of glutamate dehydrogenase

• Published in: Analytica chimica acta Vol. 411; no. 1; pp. 45 - 49
• Main Authors: Ghous, T, Townshend, A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2000; Elsevier
• Subjects: Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Enzyme inhibition; Flow injection; Fundamental and applied biological sciences. Psychology; Glutamate dehydrogenase; Proteins; Spectrophotometry; Thyroxine; Glutamate dehydrogenase; Enzyme inhibition; Spectrophotometry; Thyroxine; Flow injection; Analysis method; Enzyme; Aminoacid derivative hormone; Thyroid hormone; Oxidoreductases; Inhibition; Quantitative analysis
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/S0003-2670(00)00729-7

Thyroxine is an important hormone and is reported to be an inhibitor of glutamate dehydrogenase (GlDH). This inhibitory effect of thyroxine is used to develop a simple and highly reproducible flow injection method for its determination. The change in NADH absorbance at 340 nm in the presence of the enzyme and thyroxine is measured on-line and related to the percent inhibition (%I) which increases with inhibitor concentration. The relative standard deviation is 1.8% for 8×10 −6 M thyroxine ( n=7) and the 3 σ limit of detection is 9×10 −7 M. The linear equation over the range 0.2–8×10 −5 M was %I=4.9+8.97×10 5 [thyroxine, M], and the correlation coefficient was 0.998 ( n=7).