Method for adding cap structures to RNA using immobilized enzymes

A method for producing capped ribonucleic acid (RNA) molecules, comprising:

• i) contacting a viral capping enzyme being immobilized onto a solid support with RNA molecules, a nucleotide, and a methyl donor under conditions suitable for forming a 5′-cap0 structure, wherein the viral capping enzyme comprises a heterodimer of a catalytic polypeptide having an amino acid sequence at least 90% identical to SEQ ID NO:
• 1 having RNA triphosphatase (TPase), guanylyltransferase (GTase) and methyltransferase (MTase) activity, and a regulatory polypeptide having an amino acid sequence at least 90% identical to SEQ ID NO:
• 2, wherein the viral capping enzyme is immobilized onto the solid support by covalent binding, wherein the covalent binding is a disulfide bridge or a thioether bond;
• and
• ii) isolating the capped RNA molecules by filtration, chromatography, or centrifugation.