3-methylcrotonic acid decarboxylase (MDC) variants

A variant of a 3-methylcrotonic acid decarboxylase (MDC) showing an improved activity in converting 3-methylcrotonic acid into isobutene relative to a parent MDC having the amino acid sequence as set forth in SEQ ID NO:

• 14, wherein said variant comprises an amino acid sequence having at least 63% sequence identity to SEQ ID NO:
• 14 with a substitution, a deletion or an insertion at a position corresponding to amino acid residue 404 of SEQ ID NO:
• 14, and wherein said variant optionally further comprises a substitution, a deletion or an insertion at one or more amino acid residues corresponding to position(s) 2, 3, 5, 6, 24, 25, 35, 36, 64, 74, 80, 85, 86, 126, 129, 154, 166, 175, 195, 196, 197, 198, 204, 208, 214, 236, 237, 238, 240, 277, 298, 302, 339, 343, 347, 350, 359, 366, 368, 390, 391, 394, 395, 396, 398, 401, 402, 403, 405, 406, 407, 408, 426, 439, 440, 441, 442, 444, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462 and 473 of SEQ ID NO:
• 14.