The Measurement of Protein Turnover in Plants

Abstract

Publisher Summary This chapter presents the measurement of protein turnover in plants, the difficulties associated with the use of labeled amino acids to determine protein turnover— metabolic pools and compartmentation, and the recycling of amino acids. It also presents the use of radioactive amino acids to measure protein turnover— calculation of the rate of protein synthesis assuming no recycling and determination of the rate of protein degradation using a metabolically active amino acid to reduce cycling. The principles of the methods and the assumptions underlying them are discussed in the chapter. The mathematical basis of the methodology has been reduced to a minimum, but workers intending to measure rates of protein degradation are strongly recommended to read the carefully reasoned review of Zak et al . The availability of radioactively labeled amino acids has facilitated the tracing of the flow of metabolites in intact cells. However, there are a number of difficulties associated with quantitative aspects of this approach. Amino acids, sequestered in different organelles, may equilibrate at quite different rates with a radioactive amino acid, but when the tissue is extracted the pools mingle and cannot be distinguished.