Conversion of undesirable,
tas
te-ac
tive compounds is crucial for using barley as a sui
table raw ma
terialfor beer produc
tion. Here, ALH1, a barley alkenal hydrogenase enzyme
tha
t reduced
the
,
ta2.gif" BORDER=0 ALIGN="middle">-unsa
tura
ted double bond of aldehydes and ke
tones, was found
to conver
t trans-2-nonenal (T2N), amajor con
tribu
tor
to
the cardboard-like flavor of aged beer. Al
though
the physiological func
tion ofALH1 in barley developmen
t remains elusive, i
t exhibi
ted high specifici
ty wi
th NADPH as a cofac
torin
the conversion of several oxylipins-including T2N,
trans-2-hexenal,
trauma
tin, and 1-oc
ten-3-one. ALH1 ac
tion represen
ts a previously unknown mechanism for T2N conversion in barley. Addi
tionalexperimen
tal resul
ts resolved
the genomic sequence for barley ALH1, as well as
the iden
tifica
tion ofa paralog gene encoding ALH2. In
teres
tingly, T2N was no
t conver
ted by purified, recombinan
t ALH2.The possibili
ty
to enhance ALH1 ac
tivi
ty in plan
ta is discussed-no
t only wi
th respec
t to
thephysiological consequences
thereof-bu
t also in rela
tion
to improved beer quali
ty.Keywords: Mal
t; beer;
tas
te s
tabili
ty; alkenal hydrogenase; nonenal; 1-oc
ten-3-one