Effects of metals on enzyme activity in plants

TLDR

Phytotoxic metal uptake by higher plants inhibits some enzymes while inducing others, with metal accumulation in enzyme compartments essential for inhibition and induction contributing to stress metabolism and oxidative reactions. The study proposes future research lines to investigate enzyme inhibition and induction at various cell membranes, especially the plasma membrane, in vivo. Enzyme inhibition mainly occurs through metal binding to sulfhydryl groups or by replacing essential metals in metalloproteins, leading to loss of catalytic activity. Induction patterns of enzymes and metal‑specific changes in isoperoxidase profiles can serve as diagnostic criteria for assessing soil phytotoxicity. Abstract.

Abstract

Abstract. Uptake of phytotoxic amounts of metal by higher plants or algae can result in inhibition of several enzymes, and in increase in activity (= induction) of others. Two mechanisms of enzyme inhibition predominate: (1) binding of the metal to sulphydryl groups, involved in the catalytic actionor structural integrity of enzymes, and (2) deficiency of an essential metal in metalloproteins or metal‐protein complexes, eventually combined with substitution of the toxic metal for the deficient element. Metal accumulation in the cellular compartment of the enzyme is a prerequisite for enzyme inhibition in vivo. The induction of some enzymes is considered to play a significant role in the stress metabolism, induced by metal phytotoxicity. Peroxidase induction is likely to be related to oxidative reactions at the biomembrane; several enzymes of the intermediary metabolism might be stimulated to compensate for metal‐sensitive photosynthetic reactions. The induction of enzymes and metal‐specific changes in isoperoxidase pattern can be used as diagnostic criteria to evaluate the phytotoxicity of soils, contaminated by several metals. Lines for future research on metal phytotoxicity are proposed, involving the study of inhibition and induction of enzymes at the different cell membranes (especially the plasmamembrane) in vivo.