ABSTRACT
Metallothioneins are a class of low molecular weight, cysteine-rich proteins binding heavy metal ions. The protective effects of the thioneins against acute effects of heavy metal toxicity on the activity of certain SH-containing enzymes have been observed. The in vitro synthesis of cadystins has been studied by using the crude cell extract of fission yeast. Cadystin synthesis is also induced by stresses other than heavy metal administration, such as cell-wall wounds or the addition of antifungal agents or chitosan or polysaccharides to the incubation medium. A highly hydrophobic compound, tetramethylthiuram disulfide and its reduced form, dimethyldithiocarbamate are antifungal reagents. These compounds are also excellent inducers of cadystin synthesis in fission yeast suggesting that some alteration of the cell surface structure is a positive induction signal for caydstin synthesis. The function of cadystin is analogous to that of metallothionein and even more directly relates to glutathione. Cadystins are induced on exposure to heavy metals and bind the metals, detoxifying them.
