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).

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).

Provided is a recombinant adeno-associated virus (rAAV) or recombinant lentivirus, comprising an expression cassette in the genome, the expression cassette comprises a polynucleotide encoding thiamine pyrophosphokinase (TPK), which is operatively linked to a promoter. Also provided are also a pharmaceutical composition comprising the rAAV or recombinant lentivirus, and use of the rAAV, recombinant lentivirus and the pharmaceutical composition in the preparation of a medicament for treating or preventing Alzheimer's disease.

A method for distinguishing or differentially diagnosing Alzheimer's disease from other neurodegenerative diseases, comprising determining the level of TPK1 protein in a sample from a subject, wherein a decrease in the level of TPK1 protein compared to a reference value indicates that the subject has Alzheimer's disease. Methods, compositions, test strips, test cards and/or kits for distinguishing or differentially diagnosing Alzheimer's disease from other neurodegenerative diseases by detecting a biomarker, wherein the methods, compositions, test strips, test cards and/or kits can specifically diagnose Alzheimer's disease.

Provided is use of thiamine pyrophosphokinase TPK as a target in the treatment of Alzheimer's disease; and AD symptoms due to the inhibited TPK can be prevented by promoting the kinase activity and/or expression level of TPK protein in brain with TPK as a target.