Described are methods for the production of isobutene comprising the enzymatic conversion of 3-methylcrotonic acid into isobutene wherein the enzymatic conversion of 3-methylcrotonic acid into isobutene is achieved by making use of an FMN-dependent decarboxylase associated with an FMN prenyl transferase, wherein said FMN prenyl transferase catalyzes the prenylation of a flavin cofactor (FMN or FAD) utilizing dimethylallyl phosphate (DMAP) into a flavin-derived cofactor, wherein said method further comprises providing said DMAP enzymatically by: (i) the enzymatic conversion of dimethylallyl pyrophosphate (DMAPP) into said DMAP; or (ii) a single enzymatic step in which prenol is directly enzymatically converted into said DMAP; or (iii) two enzymatic steps comprising: first enzymatically converting DMAPP into prenol; and then enzymatically converting the thus obtained prenol into said DMAP; or (iv) the enzymatic conversion of isopentenyl monophosphate (IMP) into said DMAP, or by a combination of any one of (i) to (iv). Moreover, described are methods for the production of isobutene comprising the enzymatic conversion of 3-methylcrotonic acid into isobutene wherein the enzymatic conversion of 3-methylcrotonic acid into isobutene is achieved by making use of an FMN-dependent decarboxylase associated with an FMN prenyl transferase, wherein said FMN prenyl transferase catalyzes the prenylation of a flavin cofactor (FMN or FAD) utilizing dimethylallyl pyrophosphate (DMAPP), wherein said method further comprises providing said DMAPP enzymatically by: (v) the enzymatic conversion of isopentenyl pyrophosphate (IPP) into said DMAPP; or (vi) the enzymatic conversion of dimethylallyl phosphate (DMAP) into said DMAPP; or (vii) the enzymatic conversion of prenol into said DMAPP; (viii) or by a combination of any one of (v) to (vii). Moreover, described are methods for providing said flavin cofactor enzymatically by the enzymatic conversion of riboflavin into flavin mononucleotide (FMN).