The deoxyribonucleic acid polymerases from the diatom Cylindrotheca fusiformis. Partial purification and characterization of four distinct activities.

Four extramitochondrial DNA polymerases from the marine photosynthetic diatom Cylindrotheca fusiformis were isolated and purified more than 1200-fold by chromatography on DNA-cellulose and DEAE-Sephadex. The enzymes were equally susceptible to inhibition by the thiol-blocking agents N-ethylmaleimide and p-chloromercuribenzoate, the zinc chelator o-phenathroline, and the nucleic acid interchelators ethidium bromide and acriflavin; they displayed similar pH optima, preferred activated DNA, and had strict dependence on high K+ for maximum activity. They were differentiated on the basis of their kinetic parameters, template-primer utilization and salt requirements. The four activities varied with growth stage of C. fusiformis. Activities of polymerases A and D doubled in exponential-phase cells as compared with those in stationary-phase cells, and the increase in polymerase B and chloroplast activity C was 20-40%. The relationship of the diatom polymerases to the complements in other organisms is discussed.