Steroidogenic acute regulatory, (StAR) protein is a type of globular protein, which allows it act as an active catalyst on substrates. Because the substrates on which enzymes act usually have higher molecular weights of several hundred as compared to the enzymes, only a fraction of the enzyme's surface is in contact with the substrate. This region of contact called the active site, is as a result of the protein folding itself into a tertiary structure.

Once the correct substrate has bound at the active site of the enzyme, an enzyme-substrate complex is created. The substrate is usually held in the complex by combinations of electrical attraction, hydrophobic repulsion, or hydrogen bonding between and from the amino acid; the strongest of which is the ionic/electrostatic bonding due to larger amount of ionic "R" groups in the protein structure.

So whilst all these inter-molecular interactions are possible, the strongest would be ionic bond.

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3 years ago