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#hyaluronidase

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Fertilization in mammals-l

Acrosome reaction releases enzymes such as:

Acrosome reaction is calcium-triggered exocytosis fusing outer acrosomal membrane with overlying plasma membrane releasing enzymatic contents stored during spermiogenesis. Key enzymes liberated include hyaluronidase which hydrolyzes hyaluronan matrix surrounding cumulus cells, and serine protease acrosin plus esterases that locally digest ZP glycoproteins to create penetration slit. Additional glycosidases modify sugar residues. Enzymatic dispersal allows sperm to traverse cumulus oophorus and zona barriers. Without these hydrolases sperm cannot access oolemma, rendering fertilization impossible despite normal motility, capacitation status, successful cumulus navigation and zona binding and attachment attempts.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Acrosome reaction enzymes – hyaluronidase and acrosin in penetration.

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Fertilization in mammals-iv

Enzyme aiding corona radiata penetration:

Corona radiata consists of cumulus granulosa cells embedded in hyaluronic acid-rich extracellular matrix surrounding ovulated oocyte. Sperm must disperse this layer before contacting zona pellucida. Acrosomal membrane associated hyaluronidase hydrolyzes beta-1,4 linkages of hyaluronan polymers, breaking intercellular cement and creating paths for motile sperm. This action is complemented by flagellar thrust and other proteases. Hyaluronidase activity is greatly enhanced after capacitation and is localized on sperm surface, allowing efficient penetration of cumulus oophorus without damaging oocyte, facilitating species-specific approach to zona glycoproteins.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Fertilization - corona radiata, hyaluronidase and cumulus matrix dispersal.

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