In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: We found that the above - mentioned patient and one of the diabetic kindreds with no history of Wernicke ' s encephalopathy had abnormal transketolase as determined by its Km for TPP .
### Output Text:
We found that the above - mentioned patient and one of the diabetic kindreds with no history of Wernicke ' s encephalopathy had abnormal transketolase as determined by its Km for <span class="chemical">TPP</span> . 