Altered enzymes in drug-resistant variants of mammalian tissue culture cells.

Abstract

Journal ArticleTwo selective procedures are compared in an effort to isolate variants of mouse L cells containing structural gene mutations. Among the resulting variant cloned cell lines are found two types of alterations in theenzyme hypoxanthine phosphoribosyl transferase (EC 2.4.2.8.) (1): enzyme with altered kinetic constants causing in vivo and in vitro resistance to 8-azaguanine; and (enzyme with altered heat sensitivity in vitro. These results support the view that tissue culture cell variantscan arise from structural gene mutations