Purification of GTP:α‐d‐mannose‐1‐phosphate guanyltransferase

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Abstract
The enzyme GTP:.alpha.-D-mannose-1-phosphate guanylyltransferase from porcine thyroid tissue was purified 69,900-fold on columns of blue-Sepharose, DEAE-Sepharose, phenyl-Sepharose and agarose-GTP affinity materials. Although it exhibits a tendency to aggregate, the enzyme travelled, upon sucrose velocity sedimentation, as a single oligomer with a molecular mass of 412 kDa [kilodaltons]. Michaelis constants were determined to be 1.0 .mu.M, 1.0 mM, 3.5 .mu.M and 0.4 .mu.M for GDP-.alpha.-D-mannose, pyrophosphate, GTP and mannose-1-phosphate, respectively. The enzyme appears to be specific for the mannose moiety but will accept an inosine replacement for guanine and a deoxyribose replacement for ribose in GTP.