Discovery and development of direct thrombin inhibitors the binding site for the globular amino-terminal domain and exosite 1 is the binding site for the acidic carboxy-terminal domain of hirudin. Native hirudin, a 65-amino-acid polypeptide, is produced in the parapharyngeal glands of medicinal leeches. Hirudins today are produced by recombinant biotechnology using yeast. These recombinant hirudins lack a sulfate group at Tyr-63 and are therefore called desulfatohirudins. They have a 10-fold lower binding affinity to thrombin compared to native hirudin, but remain a highly specific inhibitor of thrombin and have an inhibition constant for thrombin in the picomolar range. Renal clearance and degradation account for the most part
Traditional Chinese medicine some cases could be confirmed by modern research (i.e., in scorpion); in some cases it couldn't (i.e., in "Curculigo"). Traditional herbal medicines can contain extremely toxic chemicals and heavy metals, and naturally occurring toxins, which can cause illness, exacerbate pre-existing poor health or result in death. Botanical misidentification of plants can cause toxic reactions in humans. The description on some plants used in traditional Chinese medicine have changed, leading to unintended intoxication of the wrong plants. A concern is also contaminated herbal medicines with microorganisms and fungal toxins, including aflatoxin. Traditional herbal medicines are sometimes contaminated with toxic heavy metals,