Release of nucleotide-cleaving phosphatase from carrot cell grown in suspension culture.

Higher plants contain unspecific phosphatases which can hydrolyse a wide variety of phosphate esters including sugar phosphates, nucleotides and phosphoenolpyruvate (Shaw 1966, Matile 1975). These enzymes can be released by plant tissue culture into the culture medium (Straus and Campbell 1963). Also terminal pyrophosphate bonds are hydrolysed by these enzymes (Shaw 1966, Hirasawa et al. 1979). While studying polydeoxyribonucleotide synthesis in cultured carrot cells it was found that deoxyribonucleoside 5'-triphosphates were hydrolysed and used as DNA precursors by intact cells at a rate approaching that of deoxyribonucleotides. This behaviour is different from that of bacteria and mammalian cells which are not able to rapidly utilize exogenous deoxyribonucleotides as DNA precursors. In this report we show that phosphohydrolases are excreted into the medium by carrot cell suspension cultures, and thus they are responsible for a rapid transformation of nucleotides into permeable compounds, which can be taken up by the cell and incorporated into DNA.