Broad-range and binary-range acyl-acyl-carrier protein thioesterases suggest an alternative mechanism for medium-chain production in seeds.
Plant Physiol
; 114(2): 669-77, 1997 Jun.
Article
en En
| MEDLINE
| ID: mdl-9193098
ABSTRACT
In the current model of medium-chain (C8-14) fatty acid biosynthesis in seeds, specialized FatB acyl-acyl-carrier-protein (ACP) thioesterases are responsible for the production of medium chains. We have isolated and characterized FatB cDNAs from the maturing seeds of elm (Ulmus americana) and nutmeg (Myristica fragrans), which accumulate predominantly caprate (100)- and myristate (140)-containing oils, respectively. In neither species were we able to find cDNAs encoding enzymes specialized for these chain lengths. Nutmeg FatB hydrolyses C14-18 substrates in vitro and expression in Brassica napus seeds leads to an oil enriched in C14-18 saturates. Elm FatB1 displays a binary specificity one activity is centered on 100-ACP, and a second is centered on palmitate (160)-ACP. After expression in B. napus seeds the oil is enriched in C10-18 saturates, predominantly 160, 140, and 100. The composition of free fatty acids produced by elm FatB1 in Escherichia coli shifts from C14-16 to mostly C8-10 by increasing the rate of chain termination by this enzyme. These results suggest the existence of an alternative mechanism used in the evolution of medium-chain production, a model of which is presented.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Proteínas de Plantas
/
Semillas
/
Tioléster Hidrolasas
/
Ácidos Grasos
Idioma:
En
Revista:
Plant Physiol
Año:
1997
Tipo del documento:
Article
País de afiliación:
Estados Unidos