A strain of
Aerobacter aerogenes
PRL-R3 has been isolated which utilizes
d
-apiose as its sole source of carbon. A new enzyme,
d
-apiose reductase, was discovered in this strain. The enzyme was not present when the strain was grown on
d
-glucose.
d
-Apiose reductase catalyzes the nicotinamide adenine dinucleotide-dependent interconversion of
d
-apiose and
d
-apiitol. The enzyme is specific for
d
-apiose and
d
-apiitol, with a few possible exceptions. The
K
m
for
d
-apiose is 0.02
m
. The
K
m
for
d
-apiitol is 0.01
m
. The enzyme is almost completely specific for the reduced and oxidized forms of nicotinamide adenine dinucleotide. When cell-free extracts were centrifuged at 100,000 ×
g
for 1 hr, the enzyme remained in solution. Optimal activity for the reduction of
d
-apiose was obtained at
p
H 7.5 in glycylglycine buffer, whereas for the oxidation of
d
-apiitol it was obtained at
p
H 10.5 in glycine buffer. Enzymatic reduction of
d
-apiose was not appreciably affected by the presence of 0.02
m
ethylenediaminetetraacetate. Paper chromatography and specific spray reagents were used to identify
d
-apiitol and
d
-apiose as the products of this reversible reaction.
d
-Apiose and
d
-apiitol did not serve as substrates for ribitol dehydrogenase and
d
-arabitol dehydrogenase from
A. aerogenes
PRL-R3.
一株利用d-阿皮酮作为唯一碳源的气生芽孢杆菌PRL-R3菌株已经被分离出来。在该菌株中发现了一种新的酶,d-阿皮酮还原酶。当该菌株在d-葡萄糖上生长时,该酶不存在。d-阿皮酮还原酶催化以烟酰胺腺嘌呤二核苷酸为依托的d-阿皮酮和d-阿皮醇之间的相互转化。该酶对d-阿皮酮和d-阿皮醇具有特异性,但也有一些例外。d-阿皮酮的Km为0.02m,d-阿皮醇的Km为0.01m。该酶对烟酰胺腺嘌呤二核苷酸的还原和氧化形式具有几乎完全的特异性。当细胞提取物以100,000×g离心1小时时,该酶仍然溶解在溶液中。在甘氨酰甘氨酸缓冲液中,d-阿皮酮还原的最佳活性在pH 7.5处获得,而在甘氨酸缓冲液中,d-阿皮醇氧化的最佳活性在pH 10.5处获得。存在0.02m乙二胺四乙酸对d-阿皮酮的酶促还原作用影响不大。使用纸层析和特异性喷雾试剂鉴定了d-阿皮醇和d-阿皮酮是该可逆反应的产物。d-阿皮酮和d-阿皮醇不是气生芽孢杆菌PRL-R3菌株中的核糖醇脱氢酶和阿拉伯糖醇脱氢酶的底物。