Egg-yolk trypsin inhibitor identical to albumen ovomucoid

Italian Journal of Zoology

Safi

2015

The egg white and egg yolk are the two main sources of nutrients for the developing avian embryo. The egg white should be transferred into the yolk in order to be consumed by the embryo. How the egg white ultimately reaches the egg yolk is largely unexplored in the turkey Meleagris gallopavo. Here, we explored the routes of egg white transfer in fertilized turkey eggs. Initially, we tested the electrophoretic pattern of the proteins in different egg compartments throughout development. Then, we used lysozyme as a reference protein to follow the egg white transfer, and we measured its activity using Micrococcus lysodeikticus as a substrate. We found that several presumptive egg white protein bands appeared in the different egg compartments. Also, the electrophoretic patterns in the intestinal fluid and thick yolk were marked by the disappearance of large bands and the appearance of small ones at late developmental stages. Moreover, we detected a chronological appearance of lysozyme activity in the different egg compartments. The activity appeared in the extraembryonic and amniotic fluids on day 15, in the intestinal fluid on day 16 and in the thick yolk on day 17, and it increased in general with the progress of development. Our results suggest that the main route of egg white transfer is albumen sac -extraembryonic cavity -amniotic cavity -intestinal lumen -egg yolk. Furthermore, the transferred egg white proteins seem to undergo digestion in the intestinal lumen and egg yolk at late developmental stages.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Transfer of egg white proteins with reference to lysozyme during the development ofMeleagris gallopavo(Galliformes: Phasianidae) embryos

Italian Journal of Zoology

Safi

2015

“…The egg yolk consists of nearly 50% water, 33% fat, 15% protein, less than 1% carbohydrate, and the rest of various minerals and vitamins (Shenstone 1968;Vieira 2007). Egg white is ultimately transferred into the yolk before being consumed by the developing embryo (Saito et al 1965;Saito & Martin 1966;Baintner & Fehér 1974;Sugimoto et al 1978Sugimoto et al , 1984Sugimoto et al , 1989Sugimoto et al , 1999Burley & Vadehra 1989;Yoshizaki et al 2002Yoshizaki et al , 2004Ito et al 2003;Shbailat & Safi 2015). In chicken, the major transfer of egg white into the yolk through the amniotic sac and intestinal lumen of the embryo occurred after day 12 (McIndoe 1960;Saito et al 1965;Saito & Martin 1966;Carinci & Manzoli-Guidotti 1968;Baintner & Fehér 1974;Burley & Vadehra 1989;Sugimoto et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Protease activity in the egg yolk during the development of Meleagris gallopavo (Galliformes: Phasianidae) embryos

Italian Journal of Zoology

Qanadilo

Alsoubani

2016

The egg white and egg yolk are the two main sources of nutrients for the developing avian embryo. Egg white ultimately reaches egg yolk before being consumed by the embryo. Previously, in the turkey Meleagris gallopavo, we showed that the major egg white transfer into the yolk through the amnion and intestinal lumen of the embryo started on day 17 and became obvious on day 19. We also suggested that the transferred egg white and endogenous yolk proteins undergo digestion at late developmental stages. However, the protease activity throughout development and the type of activated proteases are completely unexplored in the yolk of turkey eggs. Here, we measured the general proteolytic activity in the egg yolk during different developmental stages using casein as a substrate. Furthermore, we determined the type of activated proteases by employing different types of protease inhibitors. Protease activity in the egg yolk was basal throughout development until day 19 when activity significantly increased, remaining high thereafter. Moreover, acidic aspartic protease(s) were primarily activated in the yolk. Our results suggest that the transferred egg white and endogenous yolk proteins are mostly degraded by the aspartic proteases that become highly activated late in development.

Fate of egg proteins during the development of Columba livia domestica embryo

Aslan

2018

J Exp Zool Pt B

The transfer of egg white into the yolk and consumption of yolk proteins by the embryo are largely unexplored in the pigeon Columba livia domestica. Here, we investigated the route of egg white transfer as well as the degradation and uptake of yolk proteins by the pigeon embryo. Initially, we tested the electrophoretic patterns of proteins in different egg compartments throughout development. Then, we used lysozyme as a reference protein to follow the egg white transfer, and we measured its activity using Micrococcus lysodeikticus as a substrate. Moreover, we determined the general protease activity during different developmental stages in the yolk using casein. Finally, we examined the expression of aminopeptidase-N (APN) and oligopeptide transporter PepT1 genes in the yolk sac membrane (YSM) from incubation day 8 until day 17. Several electrophoretic bands of presumptive egg white proteins appeared in different egg compartments. Also, lysozyme activity was detected chronologically in the egg compartments. It appeared on day 12 in the amniotic and intestinal fluids and on day 14 in the yolk. Moreover, protease activity in the yolk increased significantly on day 14 and thereafter. APN expression was largest on day 8 and reduced generally afterward, whereas PepT1 expression peaked between days 13 and 15 but then reduced substantially. Our results suggest that the egg white proteins move through the amnion and intestine into the yolk where they undergo degradation by the activated proteases. Furthermore, the YSM appears to have a role in protein consumption, and this role decreases toward hatch.