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Recently, two DNA polymerases (ScA and ScB) were isolated and characterized from Spiroplasma citri. We now have found a third DNA polymerase (ScC) not only in S. citri but also in the serologically related honeybee spiroplasma BC3 and the unrelated flower spiroplasma BNR1. Enzyme ScC is N-ethylmaleimide (NEM) sensitive. The three DNA polymerases from the honeybee spiroplasma seem to be similar to the respective enzymes of S. citri. However, whereas the NEM-resistant enzyme ScA from S. citri and that from the BC3 honeybee spiroplasma are retained on DEAE-cellulose and require 0.09 M KCl for elution, the NEM-resistant enzyme A from the flower spiroplasma BNR1 is not retained.

The separation and partial characterization of two deoxyribonucleic acid polymerases from Spiroplasma citri have been achieved. The two enzymes had different elution properties on diethylaminoethyl (DEAE) cellulose and differed in their sensitivity to N-ethylmaleimide (NEM), preference for different template-primers, and sedimentation velocity in linear glycerol gradients. The first enzyme activity, ScA, was retained on DEAE-cellulose and was not inhibited by NEM. Activated deoxyribonucleic acid and poly(dA)-oligo(dT12) were the preferred template-primers. Arabinosyl-cytidine triphosphate had no effect. The sedimentation coefficient of ScA was 6.3s. The second activity, ScB, was not retained on DEAE-cellulose and was inhibited by NEM. Poly(dA)-oligo(dT12) was the preferred template-primer, whereas activated DNA was only poorly utilized. ScB was not affected by arabinosyl-cytidine triphosphate, and its sedimentation coefficient was 4.4s. The polymerization activities of the two enzymes were maximum at 37 to 40 degrees C.