3E81 TRANSFERASE, 2-KETO-3-DEOXYNONONIC ACID 9-PHOSPHATE PHOSPHOHYDROLASE, NUCLEOTIDYLTRANSFERASE STRUCTURE-FUNCTION ANALYSIS OF 2-KETO-3-DEOXY-D-GLYCERO-D- GALACTO-NONONATE-9-PHOSPHATE (KDN) PHOSPHATASE DEFINES A NEW CLAD WITHIN THE TYPE C0 HAD SUBFAMILY