In vitro conversion of ß-carotene to retinal in bovine rumen fluid by a recombinant ß-carotene- 15, 15'-monooxygenase.
Pasture-fed cattle yield carcasses with yellow fat; consumers often reject the resulting meat products because they assume they come from old and/or culled animals. Recombinant bacteria expressing beta-carotene 15, 15'-monooxygenase, introduced into the rumen of the animal, might help to reduce the coloration since this enzyme converts carotene to retinal, thereby eliminating the source of yellowness. The goal of this work was to evaluate the effect of a recombinant beta-carotene 15, 15'-monooxygenase (BCMO1) from Gallus gallus, expressed in Escherichia coli. The genetically modified microbe was introduced into ruminal fluid, and carotene conversion to retinal was measured. Under optimum conditions the enzyme produced 6.8 nmol of retinal per 1 mg of protein in 1 hour at 37 °C. The data on in vitro digestibility in ruminal fluid showed no differences in beta-carotene breakdown or in retinal production (p > 0.1) between E. coli with pBAD vector alone and E. coli with pBAD/BCMO1. The pBAD/BCMO1 plasmid was stable in E. coli for 750 generations. These results indicate that the protein did not break beta-carotene into retinal in ruminal fluid, perhaps due to its location in the periplasmic space in E. coli. Future research must consider strategies to release the enzyme into the rumen environment.
Programa de Posgrado en Ciencias de la Producción y de la Salud Animal, Universidad Nacional Autónoma de México, México.
Esperanza
E
García-López
Adriana
A
González-Gallardo
Anaid
A
Antaramián
María Laura
ML
González-Dávalos
Armando
A
Shimada
Alfredo
A
Varela-Echavarria
Ofelia
O
Mora
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001826:Body Fluids / Q000378:metabolism; D002417:Cattle; D002645:Chickens / Q000235:genetics; D004063:Digestion; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D012172:Retinaldehyde / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism*; D014169:Transformation, Bacterial / Q000235:genetics; D019207:beta Carotene / Q000378:metabolism*
D011994:Recombinant Proteins; D019207:beta Carotene; D006899:Mixed Function Oxygenases; C079232:beta-carotene hydroxylase; D012172:Retinaldehyde